Liquid for electrophoretic display and display medium and display employing it

ABSTRACT

A medium for electrophoretic display using a liquid for electrophoretic display which can reversibly change a visible state by action of an electric field includes a medium comprising each independent structures of microcapsules or cells filled with a liquid for electrophoretic display comprising at least alkylpolyetheramine having a structural unit represented by a specific structural formula, one or more kinds of fine particles, a dispersant and a dispersion liquid medium, wherein the fine particles contain fine particles subjected to surface treatment for making lipophilic. Also, an electrophoretic display device includes a display device comprising a pair of substrates in which a light-transmitting electrode is formed on at least one substrate and the medium for electrophoretic display described above between the substrates. The electrophoretic display medium and the electrophoretic display device each using the above display liquid for electrophoretic display have a high contrast on a display face and can display the contrast with high reliability even in repetitive display, and they are excellent as well in a response.

TECHNICAL FIELD

The present invention relates to a display liquid for electrophoreticdisplay which can reversibly change a visible state by action of anelectrical field and a display medium and a display device each usingthe same.

BACKGROUND ART

In recent years, demands for reduction in electric power consumption,reduction in a thickness and flexibility of display devices areincreased as information devices develop, and research and developmentof display devices which meet the above demands are actively carriedout.

An electrophoretic display device invented by Harold D. Lees et al. isknown as one of such display devices. This electrophoretic displaydevice has a structure in which two electrode substrates at least one ofwhich is transparent are oppositely disposed via suitable spacers and inwhich a display liquid prepared by dispersing fine particles (pigmentparticles) in a dispersion medium that is colored differently from thecolor of the particles is filled into the space between the electrodesubstrates to form a display panel, and display is shown on thetransparent electrode surface by applying an electric field to thedisplay panel (refer to, for example, patent document 1).

A liquid for electrophoretic display filled into the space between theelectrode substrates is constituted from fine particles of titaniumoxide and the like (pigment particles), a dispersion medium having a lowdielectric constant such as xylene, tetrachloroethylene, paraffin andsilicone oil in which a dye for giving a contrast of a color to the fineparticles is dissolved, a dispersant such as a surfactant and the likeand additives such as a charge-providing agent and the like. The fineparticles in the display liquid transfer to a transparent electrode sideby applying an electric field to the liquid for electrophoretic displayto allow the color of the fine particles to appear on the display face.Further, the fine particles transfer to an opposite side by applying anelectric field of a direction which is reverse to the above to allow thecolor of the dispersion medium colored by the dye to appear on thedisplay face.

Such an electrophoretic display device is a display device in whichdesired display can be obtained by controlling a direction of anelectric field, and it has the advantages that it costs low and has as abroad visibility angle as those of printed matters and that it is smallin electric power consumption and has a memory property of display, sothat it is paid attentions as an inexpensive display device.

However, since a display liquid for the above electrophoretic displaydevice described in the patent document 1 is prepared usually bydispersing an inorganic pigment having a high refractive index such astitanium dioxide and the like in a hydrophobic dispersion medium havinga low dielectric constant which is colored by dissolving a dye, it isdifficult to control dispersion stability, and it has the defects thatcoagulation brings about reduction in the contrast and the repetitivedisplay characteristics and reduction in the display quality. Further,since the dye solution is used, it has the defect that the contrast isweakened by adsorption of the dye onto the pigment surfaces.

Accordingly, a lot of developments for stabilizing the dispersionsystems and improving the display characteristics has so far been madein order to solve the above problems.

For example, an art in which sorbitan fatty acid ester surfactants areadded in a system using electrophoretic particles subjected to surfacetreatment with a coupling agent of titanate in a dispersion mediumcolored by a dye is known as a means for raising the dispersionstability (refer to, for example, patent document 2).

Further, it is known that one of two kinds of electrophoretic particleshaving different charging states is treated with a quaternary ammoniumsalt compound and a surfactant is further added thereto (refer to, forexample, patent document 3).

On the other hand, it is known as a means for improving the contrastthat a dye which is non-adsorptive to a pigment surface is used as a dyeused for coloring a dispersion medium (refer to, for example, non-patentdocument 1) and that a dye concentration in a dispersion medium is to below (refer to, for example, non-patent document 2).

Further, a method in which microcapsules encapsulated a display liquidfor electrophoretic display are used as display particles (refer to, forexample, patent document 4) is known as a method for preventing unequaldisplay caused by uneven distribution of electrophoretic fine particleson a display face.

However, the art described in the patent document 2 is unsatisfactory inan effect of dispersion stabilization and still has a problem in that asatisfactory effect is not obtained as well in a contrast of display.

Also, a satisfactory dispersion stability is not obtained as well in theart described in the above patent document 3, and the effect isunsatisfactory.

Further, the methods described in the non-patent documents 1 and 2 donot come to completely solve the defects brought about by the dyesolutions and still have problems in terms of practical use.

In the method of the patent document 4 described above, a colored dyesolution and a dispersion liquid of pigment particles are used for anencapsulated display liquid, and therefore it is not satisfactory interms of a contrast as is the case with the phenomenon described above.

Then, an electrophoretic display device in which a dye solution is notused is known as a means for solving the problems involved in thesystems in which a dispersion medium colored by dyes is used. Known is,for example, an electrophoretic display element in which a liquidprepared by dispersing at least two kinds of electrophoretic fineparticles which are different from each other in a color tone and anelectrophoretic property in a colorless dispersion medium is filled in acell formed between two counter electrodes at least one of which istransparent via spacers (refer to, for example, patent document 5).

Also, use of a steric repulsion effect brought about by addition of acharge-controlling agent and surface treatment of particles is known asa means for preventing coagulation between particles which is a problemin a system using, as a display liquid for electrophoretic display, theabove liquid prepared by dispersing two kinds of the electrophoreticfine particles which are different from each other in a color tone andan electrophoretic property (electrified charge) (refer to, for example,patent document 6).

Further, known is an electrophoretic display element using a liquidprepared by dispersing at least two kinds of electrophoretic fineparticles which have the same electrophoretic property and which aredifferent from each other in an electrophoretic speed in a colorlessdispersion medium (refer to, for example, patent document 7).

Also, known is a display liquid for electrophoretic device containingparticles which are subjected to surface treatment and have voids in theinside and pigment particles having a color tone which is different fromthat of the above particles in a dispersion medium (refer to, forexample, patent document 8).

Further, known as well is an art in which a liquid prepared bydispersing at least two kinds of electrophoretic fine particles whichare different from each other in a color tone and an electrophoreticproperty in a colorless dispersion medium is encapsulated inmicrocapsules (refer to, for example, patent document 9).

However, in the art described in the patent document 5 described above,an electrified charge of the different electrophoretic fine particles iscombination of a positive charge and a negative charge, and thereforeinvolved therein is the problem that electric attracting force isproduced between the fine particles to cause coagulation of the fineparticles, whereby the dispersion stability is reduced to bring aboutdeterioration in the contrast by mixed color.

Also, in the art described in the patent document 6 described above,involved therein is the problem that it is difficult to completelyprevent two kinds of the electrophoretic fine particles from beingcoagulated, so that the good contrast can not be realized.

Further, even the fine particles having a slow moving speed described inthe above patent document 7 are in a shorter moving distance whenpresent close to the electrode on the display face and therefore appearon the display face in a certain case. Also, an electrified charge isusually different even between particles having the same color tone, andthe moving speeds have distribution. Accordingly, a problem is involvedin that it is difficult to obtain the satisfactory contrast withoutcontrolling so that the particles are not superposed among those havingdifferent color tones.

Further, in the particles having voids in the inside described in theabove patent document 8, the dispersion liquid medium gets into thevoids, and therefore particularly the white particles are reduced in arefractive index, which makes it difficult to obtain the satisfactorycontrast.

Also in the case described in the above patent document 9, stability ofthe dispersion liquid is not maintained, and there still remains theproblem that color mixing caused by coagulation due to electricattracting force between the electrophoretic fine particles is generatedin the microcapsule to bring about color mixing of display.

Patent document 1: U.S. Pat. No. 3,612,758 (claims, examples and others)

Patent document 2: U.S. Pat. No. 2,733,687 (claims, examples and others)

Patent document 3: Japanese Patent Application Laid-Open No. 119704/1999(claims, examples and others)

Non-patent document 1: Philips Lab: Conference Record of 1980 BiennialDisp. Res. Conf.

Non-patent document 2: Xerox Palo Alto: Proc. SID, Vol. 18 3/4, 1977

Patent document 4: Japanese Patent No. 2551783 (claims, examples andothers)

Patent document 5: Japanese Patent Application Laid-Open No. 269124/1987(claims, examples and others)

Patent document 6: Published Japanese translation of PCT InternationalPublication for Patent Application No. 5101190/1996 (claims, examplesand others)

Patent document 7: Japanese Patent Application Laid-Open No. 50886/1988(claims, examples and others)

Patent document 8: U.S. Patent Application No. 2002-277903 (claims,examples and others)

Patent document 9: U.S. WO98/03896 (claims, examples and others)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In light of the problems of the conventional art described above and theexisting situation, the present invention intends to solve them, and anobject thereof is to provide a liquid for electrophoretic display whichcan realize display having a high contrast by improving dispersionstability of the liquid for electrophoretic display and can display acontrast with high reliability even in repetitive display and which isexcellent in a response, a display medium and a display device eachusing the same.

Means for Solving the Problems

Intensive investigations on the problems of the conventional artdescribed above repeated by the present inventors have resulted infinding that a liquid for electrophoretic display which meets the objectdescribed above, and a display medium and a display device each usingthe same are obtained by adding a specific component to a liquidcomprising one or more kinds of fine particles, a dispersant and adispersion liquid medium, and thus the present invention has come to becompleted.

That is, the present invention comprises the following items (1) to(24).(1) A liquid for electrophoretic display comprising at leastalkylpolyetheramine having a structural unit represented by thefollowing Formula (I), one or more kinds of fine particles, a dispersantand a dispersion liquid medium, wherein the fine particles describedabove contain fine particles subjected to surface treatment for makinglipophilic:

in Formula (I) described above, R₁ is a saturated hydrocarbon group oran unsaturated hydrocarbon group; R₂ is (CH₂CH₂O)x-H; R₃ is(CH₂CH₂O)y-H; and x and y are positive numbers.(2) A liquid for electrophoretic display comprising at leastalkylpolyetheramine having a structural unit represented by thefollowing Formula (I), a polyoxyethylene oxypropylene block polymerhaving a structural unit represented by the following Formula (II), oneor more kinds of fine particles and a dispersion liquid medium:

in Formula (I) described above, R₁ is a saturated hydrocarbon group oran unsaturated hydrocarbon group; R₂ is (CH₂CH₂O)x-H; R₃ is(CH₂CH₂O)y-H; and x and y are positive numbers;OH(C₂H₄O)p(C₃H₆O)qH  (II)in Formula (II) described above, p and q are positive numbers.(3) The liquid for electrophoretic display as described in the aboveitem (2), further comprising an acetylene derivative having a structuralunit represented by the following Formula (III):

in Formula (III) described above, R₄ and R₅ are a saturated hydrocarbongroup or an unsaturated hydrocarbon group; R₆ is OCH₂CH(CH₃)— or(OCH₂CH₂)m-OH; R₇ is OCH₂CH(CH₃)— or (OCH₂CH₂)n-OH; m and n are 0 orpositive numbers; and R₆ and R₇ may be the same or different.(4) The liquid for electrophoretic display as described in the aboveitem (2) or (3), wherein the polyoxyethylene oxypropylene block polymerhas an average molecular weight of 1000 to 4000.(5) The liquid for electrophoretic display as described in any one ofthe above items (2) to (4), wherein an amount of ethylene oxide in thepolyoxyethylene oxypropylene block polymer is 50% by weight or less.(6) The liquid for electrophoretic display as described in any one ofthe above items (2) to (5), wherein a content of the polyoxyethyleneoxypropylene block polymer is 0.01 to 30% by weight based on the totalamount of the display liquid.(7) The liquid for electrophoretic display as described in any one ofthe above items (3) to (6), wherein an HLB of the acetylene derivativeis 10 or less.(8) The liquid for electrophoretic display as described in any one ofthe above items (2) to (7), wherein the fine particles are subjected tosurface treatment for making lipophilic.(9) The liquid for electrophoretic display as described in any one ofthe above items (1) to (8), wherein the surface treatment for makinglipophilic is carried out with a coupling agent.(10) The liquid for electrophoretic display as described in the aboveitem (9), wherein the coupling agent is at least one selected from thegroup consisting of titanate base coupling agents, aluminum basecoupling agents and silane base coupling agents.(11) The liquid for electrophoretic display as described in any one ofthe above items (1) to (10), wherein a surface functional group of thefine particles subjected to the surface treatment for making lipophilicis an alkoxycarbonyl group.(12) The liquid for electrophoretic display as described in any one ofthe above items (1) to (11), wherein a content of thealkylpolyetheramine is 1.0 to 200% by weight based on a content of thefine particles.(13) The liquid for electrophoretic display as described in any one ofthe above items (1) to (12), wherein at least one kind of the fineparticles is polymer fine particles containing a colorant, an organicpigment or an inorganic pigment.(14) The liquid for electrophoretic display as described in the aboveitem (13), wherein a structural component of the polymer fine particlescontaining a colorant is a cross-linked acryl base resin.(15) The liquid for electrophoretic display as described in any one ofthe above items (1) to (14), wherein the fine particles have a meanparticle size of 0.05 to 20 μm.(16) The liquid for electrophoretic display as described in any one ofthe above items (2) to (15), further comprising a dispersant.(17) The liquid for electrophoretic display as described in any one ofthe above items (1) to (16), wherein the dispersant is a nonionic oranionic surfactant.(18) The liquid for electrophoretic display as described in any one ofthe above items (1) to (17), wherein a content of the dispersant is 0.01to 50% by weight based on the total amount of the display liquid.(19) A medium for electrophoretic display characterized by that theliquid for electrophoretic display as described in any one of the aboveitems (1) to (18) is filled into each independent structures ofmicrocapsules or cells.(20) The medium for electrophoretic display as described in the aboveitem (19), wherein in the structure of the cell filled with the liquidfor electrophoretic display, an electrode part and a cell part withwhich the liquid for electrophoretic display is brought into contact aresubjected to hydrophilization treatment selected from the groupconsisting of ozone treatment, plasma treatment, corona treatment, UVitoro treatment, sputtering treatment, polymer layer-forming treatment,inorganic layer-forming treatment and organic or inorganic hybridlayer-forming treatment.(21) The medium for electrophoretic display as described in the aboveitem (19), wherein the microcapsule has a size of 10 to 200 μm.(22) The medium for electrophoretic display as described in the aboveitem (19) or (21), wherein the microcapsule has flexibility and is lessliable to produce a gap in arranging the microcapsules.(23) The medium for electrophoretic display as described in any one ofthe above items (19) to (22), wherein the independent cells have avolume of 1×10⁻⁹ to 1×10⁻³ ml.(24) An electrophoretic display device comprising a pair of substratesin which a light-transmitting electrode is formed on at least onesubstrate and the medium for electrophoretic display as described in anyone of the above items (19) to (23) interposed between the abovesubstrates.

Effects of the Invention

According to the present invention, provided are a liquid forelectrophoretic display which provides a high contrast on a display faceand can display a contrast with high reliability even in repetitivedisplay and which is excellent in a response, a display medium and adisplay device each using the same.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is an explanatory drawing of a titanium oxide fine particle asurface of which is treated with a titanate coupling agent.

FIG. 2 is a drawing schematically showing an embodiment in which theliquid for electrophoretic display of a single particle type is filledinto a structure comprising a microcapsule.

FIG. 3 is a drawing schematically showing an embodiment in which theliquid for electrophoretic display of a double particle type is filledinto a structure comprising a microcapsule.

FIG. 4 is a drawing schematically showing one example of an embodimentin which the liquid for electrophoretic display is filled into astructure comprising a cell.

FIG. 5 is a drawing schematically showing another example of theembodiment in which the liquid for electrophoretic display is filledinto a structure comprising a cell.

FIG. 6 is a drawing schematically showing the other example of theembodiment in which the liquid for electrophoretic display is filledinto a structure comprising a cell.

FIG. 7 is a cross-sectional drawing schematically showing one example ofan embodiment in which microcapsules are disposed between counterelectrodes.

FIG. 8 is a cross-sectional drawing schematically showing one example ofan embodiment in which a cell structure sheet is disposed betweencounter electrodes.

FIG. 9 is a cross-sectional drawing schematically showing anotherexample of the embodiment in which a cell structure sheet is disposedbetween counter electrodes.

FIG. 10 is a schematic drawing of an electrophoretic display deviceusing a display medium prepared by filling a structure comprisingmicrocapsules with the liquid for electrophoretic display of a singleparticle type.

FIG. 11 is a schematic drawing of an electrophoretic display deviceusing a display medium prepared by filling a structure comprisingmicrocapsules with the liquid for electrophoretic display of a doubleparticle type.

FIG. 12 is a cross-sectional drawing showing one example of use state ofan electrophoretic display device.

EXPLANATION OF NUMERALS

-   1 Titanium oxide fine particles subjected to treatment for making    lipophilic-   2 Black solvent-   3 Capsule wall-   10 Transparent electrode-   11 Binder resin layer-   12 Microcapsule-   13 Counter electrode-   14 Cell-forming sheet

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention shall be explained below indetails invention by invention.

The liquid for electrophoretic display according to the presentinvention is constituted from the respective liquids for electrophoreticdisplay which are the first invention to the third invention. To bespecific, the liquid for electrophoretic display according to the firstinvention is characterized by comprising at least alkylpolyetheraminehaving a structural unit represented by the following Formula (I), oneor more kinds of fine particles, a dispersant and a dispersion liquidmedium, wherein the fine particles contain fine particles subjected tosurface treatment for making lipophilic:

in Formula (I) described above, R₁ is a saturated hydrocarbon group oran unsaturated hydrocarbon group; R₂ is (CH₂CH₂O)x-H; R₃ is(CH₂CH₂O)y-H; and x and y are positive numbers.

Further, the liquid for electrophoretic display according to the secondinvention is characterized by comprising at least alkylpolyetheraminehaving a structural unit represented by Formula (I) described above, apolyoxyethylene oxypropylene block polymer having a structural unitrepresented by the following Formula (II), one or more kinds of fineparticles and a dispersion liquid medium, and the liquid forelectrophoretic display according to the third invention ischaracterized by further comprising an acetylene derivative having astructural unit represented by the following Formula (III) in additionto the liquid for electrophoretic display described above according tothe second invention:OH(C₂H₄O)p(C₃H₆O)qH  (II)in Formula (II) described above, p and q are positive numbers;

in Formula (III) described above, R₄ and R₅ are a saturated hydrocarbongroup or an unsaturated hydrocarbon group; R₆ is OCH₂CH(CH₃)— or(OCH₂CH₂)m-OH; R₇ is OCH₂CH(CH₃)— or (OCH₂CH₂)n-OH; m and n are 0 orpositive numbers; and R₆ and R₇ may be the same or different.

The alkylpolyetheramine used in the first invention to the thirdinvention is used primarily as a charge-controlling agent and may havethe structural unit represented by Formula (I) described above. Capableof being given are, for example, polyethylene glycol laurylamine,polyethylene glycol alkyl(coconut)amine, polyethylene glycolstearylamine, polyethylene glycol alkyl(beef tallow)amine,hydroxyethyllaurylamine, polyethylene glycol alkyl(deer tallow)amine,polyethylene glycol alkyl(sheep tallow)amine, polyethylene glycolalkyl(beef tallow)propylenediamine and polyethylene glycol dioleylamine.It shall not be restricted to them as long as they are dissolved atleast in the dispersion liquid medium used.

When using alkylpolyetheramine which is not included in Formula (I)described above, the contrast on the display face is weak, and thereliability in repetitive display is reduced as well. In addition, theresponse is deteriorated as well, and therefore it is not preferred.

The alkylpolyetheramine can be used alone (one kind) or in combinationof two or more kinds thereof. A content thereof is suitably determinedaccording to the kind thereof, and it is added in a range of preferably1.0 to 200% by weight (hereinafter referred to merely as “%”), morepreferably 10 to 150% based on the fine particles subjected to thesurface treatment for making lipophilic in the first invention describedlater or the fine particles of the second and third inventions.

If the above content of the alkylpolyetheramine is less than 1.0% basedon the fine particles subjected to the surface treatment for makinglipophilic in the first invention or the fine particles of the secondand third inventions, the effect of the alkylpolyetheramine is notexhibited, and the contrast on the display face is weak. The reliabilityin repetitive display is reduced as well, and the response isdeteriorated as well. On the other hand, if it exceeds 200% based on thefine particles subjected to the surface treatment for making lipophilicor the fine particles, an electroconductivity of the solvent is raised,and therefore moving of the fine particles and the contrast display arereduced. Further, that shall become a factor in which the liquid itselffor electrophoretic display is broken by electrolysis, and therefore itis not preferred.

For example, colored or colorless (white) inorganic pigment particles,organic pigment particles and polymer fine particles can be used as thefine particles used in the first invention to the third invention, andthey can be used alone (one kind) or in a mixture of two or more kindsthereof.

In the first invention, at least the fine particles subjected to thesurface treatment for making lipophilic have to be involved in the fineparticles used described above from the viewpoint of exhibiting theeffects of the present invention, and if at least one kind of the fineparticles subjected to the surface treatment for making lipophilic isinvolved therein, fine particles which are not subjected to the surfacetreatment for making lipophilic (colored or colorless (white) inorganicpigment particles, organic pigment particles and polymer fine particles)may be involved therein in addition to the above fine particlessubjected to the surface treatment for making lipophilic.

In the first invention, if the fine particles subjected to the surfacetreatment for making lipophilic are not used, the repetitive display andthe response are inferior, and stability of the liquid is deterioratedas well, so that the effects of the present invention are not exhibited.

In the second invention and the third invention, even if the fineparticles subjected to the surface treatment for making lipophilic arenot used, the effects of the present invention can be exhibited asdescribed later.

In the first invention to the third invention, the “pigment particles”described above mean particles which have low solubility in the solventused as the dispersion liquid medium and which can be present in adispersed particle state in the solvent.

The inorganic pigment particles which can be used include, for example,titanium dioxide, zinc sulfide, calcium carbonate, silica, calciumsilicate, lead white, zinc oxide, lithopone, antimony oxide, kaoline,mica, barium sulfate, gloss white, alumina white, talc, cadmium yellow,cadmium lithopone yellow, yellow iron oxide, titan yellow, titan bariumyellow, cadmium orange, cadmium lithopone orange, molybdate orange, rediron oxide, red lead, vermilion, cadmium red, cadmium lithopone red,umber, brown iron oxide, zinc iron, chromium brown, chromium green,chromium oxide, viridian, cobalt green, cobalt chromium green, titancobalt green, Prussian blue, cobalt blue, ultramarine blue, ceruleanblue, cobalt aluminum chromium blue, cobalt violet, mineral violet,carbon black, black iron oxide, manganese ferrite black, cobalt ferriteblack, copper chromium black, copper chromium manganese black, blacklow-level titanium oxide, aluminum powder, copper powder, lead powder,tin powder and zinc powder.

The organic pigment particles which can be used include, for example,fast yellow, diazo yellow, condensed azo yellow, anthrapyrimidineyellow, isoindoline yellow, copper azomethine yellow, quinophthaloneyellow, benzimidazolone yellow, nickel dioxime yellow, monoazo yellowlake, dinitoroaniline orange, pyrazolone orange, perinone orange,naphthol red, toluidine red, permanent carmine, brilliant fast scarlet,pyrazolone red, Rhodamine 6G lake, permanent red, lithol red, bon lakered, brilliant carmine, Bordeaux 10B, naphthol red, quinacridonemagenta, condensed azo red, naphthol carmine, perylene scarlet,condensed azo scarlet, benzimidazolone carmine, anthraquinonyl red,perylene red, perylene maroon, quinacridone maroon, quinacridonescarlet, quinacridone red, diketopyrrolopyrrole red, benzimidazolonebrown, phthalocyanine green, Victoria blue lake, phthalocyanine blue,fast sky blue, alkali blue toner, indanthrone blue, Rhodamine B lake,methyl violet lake, dioxazine violet and naphthol violet.

Polymer fine particles comprising organic polymers produced by knownmethods can be used as the polymer fine particles and such methodsinclude, for example, a method making use of emulsion polymerization, aseed emulsion polymerization method, a soap free polymerization method,a dispersion polymerization method, a suspension polymerization method,a seed polymerization method, a method making use of seed polymerization& polymerization contraction, a method carrying out suspensionpolymerization of a W/O/W emulsion, a method making use of dryingsurfaces of droplets in spray drying and a seed coagulation method inwhich a polymer emulsion is coagulated by adding electrolytic solidparticles. However, they shall not be restricted to those produced bythe above methods.

Those selected from polymer materials which have so far been publiclyknown and which are not dissolved in a transparent dispersion mediumused for electrophoretic display can be used as materials for thepolymer fine particles. Capable of being given as the examples thereofare polymer materials such as styrene bases, styrene-acryl bases,styrene-isobutylene bases, divinylbenzene bases, methyl methacrylatebases, methacrylate bases, ethyl methacrylate bases, ethyl acrylatebases, n-butyl acrylate bases, acrylic acid bases, acrylonitrile bases,acryl rubber-methacrylate bases, ethylene bases, ethylene-acrylic acidbases, nylon bases, silicone bases, urethane bases, melamine bases,benzoguanamine bases, phenol bases, fluorine (tetrachloroethylene)bases, vinylidene chloride bases, quaternary pyridinium salt bases,synthetic rubbers, celluloses, cellulose acetate, chitosan and calciumalginate and polymer materials which are improved in a solvent resistantfunction by cross-linking the above polymer materials. In particular,materials containing cross-linked acryl base resins as a component arepreferred from the viewpoint of a solvent resistance, but they shall notbe restricted to the above polymer materials.

Also, the above polymer fine particles may be colored with dyes andpigments by publicly known methods, such methods include, for example, amethod in which monomers are colored before synthesizing to produce thepolymer fine particles using the methods described above, a method inwhich the polymer fine particles are colored in the middle of producingthem and a method in which the polymer fine particles are colored afterproducing them.

Further, in respect to another method, dyes or pigments are physicallydispersed in the polymer materials described above which are obtained bysynthesizing in advance, and then they are crushed to the desiredparticle sizes, whereby the fine particles can be obtained. However, thecolored polymer fine particles shall not be restricted to those obtainedby the above methods.

In the present invention, the fine particles subjected to surfacetreatment for making lipophilic are those obtained by treating thesurface parts of the various fine particles described above (colored orcolorless (white) inorganic pigment particles, organic pigment particlesand polymer fine particles) with lipophilic surface treating agents.

The lipophilic surface treating agents include, for example, couplingagents, pigment derivatives and lipophilic surfactants, and the couplingagents are particularly preferably used from the viewpoints ofdispersibility and fluidity.

The coupling agents which can be used include, for example, silane basecoupling agents, titanate base coupling agents, aluminum base couplingagents, zirconium base coupling agents, zircoaluminate base couplingagents, a chromium base coupling agents and fluorine base couplingagents.

The above various coupling agents include, for example, the followingones but shall not be restricted to them.

The titanate base coupling agents include, for example,isopropyltriisostearoyl titanate, isopropyltristearoyl titanate,isopropyltrioctanoyl titanate, isopropyldimethacrylisostearoyl titanate,isopropyltridodecylbenzenesulfonyl titanate, isopropylisostearoyldiacryltitanate, isopropyltri(dioctcylphosphate) titanate,isopropyltricumylphenyl titanate, isopropyltris(dioctcylpyrophosphate)titanate, isopropyltri(n-aminoethyl-aminoethyl) titanate,tetraisopropylbis(dioctcylphosphite) titanate,tetraoctcylbis(ditridecylphosphite) titanate,tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate,dicumylphenyloxyacetate titanate, bis(dioctcylpyrophosphate)oxyacetatetitanate, diisostearoylethylene titanate,bis(dioctcylpyrophosphate)ethylene titanate,bis(dioctcylpyrophosphate)diisopropyl titanate, tetramethylorthotitanate, tetraethyl orthotitanate, tetrapropyl orthotitanate,tetraisopropyltetraethyl orthotitanate, tetrabutyl orthotitanate, butylpolytitanate, tetraisobutyl orthotitanate, 2-ethylhexyl titanate,stearyl titanate, cresyl titanate monomers, cresyl titanate polymers,diisopropoxy-bis-(2,4-pentadionate)titanium (IV),diisopropoxy-bis-triethanolamino titanate, octylene glycol titanate,titanium lactate, acetoacetic ester titanate,diisopropoxybis(acetylacetonato)titanium,di-n-butoxybis(triethanolaluminato)titanium,dihydroxybis(lactato)titanium, titanium-isopropoxyoctylene glycolate,tetra-n-butoxytitanium polymers, tri-n-butoxytitanium monostearatepolymers, butyl titanate dimers, titanium acetylacetonate, polytitaniumtitanium acetylacetonate, titanium octylene glycolate, titanium lactateammonium salt, titanium lactate ethyl ester, titanium triethanolaminateand polyhydroxytitanium stearate.

The aluminum base coupling agents include, for example,acetalkoxyaluminum diisopropylate.

The silane base coupling agents include, for example,3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane,3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane,3-aminopropyltrimethoxysilane,3-aminopropyl-tris(2-methoxy-ethoxy-ethoxy)silane,N-methyl-3-aminopropyltrimethoxysilane,N-aminoethyl-3-aminopropyl-trimethoxysilane, diaminosilane,N-aminoethyl-3-aminopropylmethyldimethoxysilane,triaminopropyl-trimethoxysilane,3-amino-4,5-dihydroimidazolepropyltriethoxysilane,3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane,3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane,3-mercaptopropylmethyldimethoxysilane, 3-chloropropyltriethoxysilane,3-chloropropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane,3-cyanopropyltriethoxysilane, vinyltrichlorosilane,vinyltriethoxysilane, vinyltrimethoxysilane,vinyltri(2-methoxyethoxy)silane, hexamethyldisilazane,N,O-bis(trimethylsilyl)acetamide, methyltrimethoxysilane,methyltriethoxysilane, ethyltrichlorosilane, n-propyltrimethoxysilane,isobutyltrimethoxysilane, amyltrichlorosilane, octyltriethoxysilane,vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane,N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane,γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane,phenyltrimethoxysilane, phenyltriethoxysilane,methyltri(methacryloyloxyethoxy)-silane, methyltri(glycidyloxy)silane,long chain alkyltriethoxysilane, tetramethyl silicate, tetraethylsilicate, vinyltris(2-methoxyethoxy)silane,3-glycidoxypropylmethyldimethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-methacryloxypropyltrimethoxysilane andγ-(2-aminoethyl)aminopropylmethyldimethoxysilane.

Further, they includeN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilanehydrochloride, vinyltriacetoxysilane, γ-anilinopropyltrimethoxysilane,octadecyldimethyl [3-(trimethyoxysilyl)propyl]ammonium chloride,γ-chloropropylmethyldichlorosilane,γ-methacryloxypropylmethyldimethoxysilane, trimethylmethoxysilane,trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane,tetramethoxysilane, tetraethoxysilane, methyldimethoxysilane,methyldiethoxysilane, dimethylethoxysilane, dimethylvinylmethoxysilane,dimethylvinylethoxysilane, methylvinyldimethoxysilane,methylvinyldiethoxysilane, diphenyldimethoxysilane,diphenyldiethoxysilane, trimethylchlorosilane, dimethyldichlorosilane,methyltrichlorosilane, methyldichlorosilane, dimethylchlorosilane,dimethylvinylchlorosilane, methylvinyldichlorosilane,methylchlorodisilane, triphenylchlorosilane, methyldiphenylchlorosilane,diphenyldichlorosilane, methylphenyldichlorosilane,phenyltrichlorosilane, chloromethyldimethylchlorosilane,hexamethyldisilazane, cyclic silazane mixtures,N,N-bis(trimethylsilyl)urea, N-trimethylsilylacetamide,dimethyltrimethylsilylamine, diethyltrimethylsilylamine,trimethylsilylimidazole and N-trimethylsilylphenylurea.

The zirconium base coupling agents include zirconium butylate, zirconiumacetylacetonate, acetylacetone zirconium butylate, zirconium lactate,stearic acid zirconium butylate, tetra(triethanolamine) zirconate andtetraisopropyl zirconate.

The zircoaluminate base coupling agents include product names A, C, C-1,F, M, M-1, S, APG, CPG, CPM, FPM, MPG and MPM each manufactured byKusumoto Chemicals, Ltd. and tetrapropyl zircoaluminate.

The chromium base coupling agents include complexes of chromiummethacrylate and chromium chloride.

The fluorine base coupling agents includetrifluoropropyltrimethoxysilane andheptadecatrifluorodecyltrimethoxysilane.

The respective coupling agents described above can be used alone (onekind), and in addition thereto, they can be used in a mixture of plural(two or more kinds) coupling agents. Further, treatments using pluralcoupling agents can be carried out by stages.

Among the respective coupling agents described above, the titanate basecoupling agents, the aluminum base coupling agents and the silane basecoupling agents are particularly preferred from the viewpoint thatexcellent effects are shown when using them.

The objects of the surface treatment by the coupling agents in the firstinvention are not only inorganic pigments but also organic materials,for example, polymer fine particles of an organic polymer base andorganic pigment particles. Materials in which the presence of activereaction sites (for example, a hydroxyl group) capable of carrying outcoupling reaction with the coupling agents is indistinct are included aswell in the above matrix particles. However, also when such matrixparticles are subjected to coupling treatment with various couplingagents, the surface characteristics of the matrix particles can bechanged by the coupling agents.

In respect to the reasons thereof, it is considered that even when areaction-active group is not present, the coupling agents are physicallyadhered to the surface of the matrix particles or impregnated into thesurface, whereby a change in the surface characteristics is realized.The treatment with the coupling agents referred to in the presentinvention includes a change in the surface characteristics describedabove.

In the present invention, the fine particles subjected to surfacetreatment for making lipophilic include, to be specific, particlesobtained by treating ITT-2 TiO₂ CR-50 (titanium oxide treated a surfacewith a titan coupling agent, mean particle size: about 0.4 μm,manufactured by Nikko Chemicals Co., Ltd.), ITT-7 TiO₂ TTO-S-3 (fineparticle titanium oxide treated a surface with a titan coupling agent,mean particle size: 0.05 to 0.1 μm, manufactured by Nikko Chemicals Co.,Ltd.), KR-380 (titanium oxide treated a surface with a lipophilicsurface treating agent, mean particle size: about 0.5 μm, manufacturedby Titan Kogyo Co., Ltd.), KR-270 (titanium oxide treated a surface witha lipophilic surface treating agent, mean particle size: about 0.4 μm,manufactured by Titan Kogyo Co., Ltd.) and Tipaque CR-50 (titanium oxidehaving a hydrophilic surface, mean particle size: about 0.4 μm,manufactured by Ishihara Sangyo Kaisha, Ltd.) with coupling agents (forexample, aluminum base coupling agents and silane base coupling agents).

FIG. 1 shows titanium oxide fine particle (ITT-2 TiO₂ CR-50) in which atitanium oxide surface is treated with a titan coupling agent.

In the first invention, the fine particles subjected to the surfacetreatment for making lipophilic described above are particularlypreferably particles in which a surface functional group is analkoxycarbonyl group from the viewpoints of enhancing dispersibility inthe dispersion medium and fluidity. The particles in which a surfacefunctional group is an alkoxycarbonyl group can be formed, for example,by eliminating an isopropyl group from isopropyl triisostearate titaniumwhich is a titan coupling agent and allowing titanium to be bonded to ahydroxyl group on a particle surface.

Various fine particles described above having the structures describedabove are used as the fine particles of the first invention to the thirdinvention, and fine particles having various particle sizes can be usedin relation to a constituent display medium. Among them, the fineparticles having a mean particle size of preferably 0.05 to 20 μm,particularly preferably 0.1 to 10 μm are used from the viewpoint offurther enhancing the display characteristic, the memory property andthe dispersion stability.

If the above mean particle size of the fine particles is less than 0.05μm, an effect of diffusion caused by a Brownian motion of the fineparticles is exerted to deteriorate the display characteristic, andcoagulation tends to be strengthened, so that the dispersion systembecomes instable. On the other hand, if the mean particle size exceeds20 μm, the fine particles are liable to settle down, and it becomes afactor for deteriorating the display memory property and the dispersionstability.

In the present invention, the fine particles subjected to surfacetreatment for making lipophilic are contained in a proportion ofpreferably 10% or more, more preferably 20 to 100% based on the totalamount of the fine particles from the viewpoint of exhibiting theeffects of the present invention.

The total content of the fine particles is preferably 3 to 50%, morepreferably 5 to 35% based on the total amount of the liquid forelectrophoretic display.

If the above content of the fine particles is less than 3%, it isdifficult to display the satisfactory contrast. On the other hand, if itexceeds 50%, interference between the fine particles is caused to reducea moving speed and a response speed. Accordingly, both the ranges arenot preferred.

When two kinds of black and white fine particles are used, thoseparticles can be used with changing a proportion of the black and whitefine particles in a range in which the total amount of both particles is3 to 50% so that a black and white contrast can sufficiently bedisplayed.

Various dispersants, surfactants and high molecular surfactants whichare conventionally used can be used as the dispersant in the firstinvention.

The specific examples of the surfactants used as the dispersant includethe following nonionic surfactants, anionic surfactants, cationicsurfactants, amphoteric surfactants and high molecular type surfactants,but they shall not be restricted to them.

The nonionic surfactants include, for example, polyoxyalkylenealkylphenol ethers such as polyoxyethylene nonylphenol ether,polyoxyethylene dinonylphenol ether, polyoxyethylene octylphenol ether,polyoxyethylene styrenated phenol, polyoxyethylene bisphenol A,polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether andnonylphenol ethoxylate, polyoxyalkylene ethers such as polyoxyethylenecastor oil, polyoxyalkylene block polymers, polyoxyethylene cetyl ether,polyoxyethylene lauryl ether, polyoxyethylene oleyl ether,polyoxyethylene stearyl ether and polyoxypropylene ether, glycols suchas polyoxyalkylene glycols of a monool type, polyoxyalkylene glycols ofa diol type, polyoxyalkylene glycols of a triol type, polyalkyleneglycols of a monool base block type, polyalkylene glycols of a diol baseblock type and polyalkylene glycols of a random type, primary linearalcohol ethoxylate and secondary linear alcohol ethoxylate such asoctylphenol ethoxylate, oleyl alcohol ethoxylate and lauryl alcoholethoxylate, alkyl alcohol ethers such as polynuclear phenol ethoxylate,polyoxyalkylene alkyl esters such as polyoxyethylene rosin ester,polyoxyethylene lauryl ester, polyoxyethylene oleyl ester andpolyoxyethylene stearyl ester, sorbitan fatty acid esters such assorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate,sorbitan dilaurate, sorbitan dipalmitate, sorbitan distearate, sorbitansesquilaurate, sorbitan sesquipalmitate, sorbitan sesquistearate,sorbitan monooleate, sorbitan dioleate, sorbitan sesquioleate andsorbitan trioleate, polyoxyethylene sorbitan esters such aspolyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan dilaurate, polyoxyethylene sorbitan dipalmitate,polyoxyethylene sorbitan distearate, polyoxyethylene sorbitansesquilaurate, polyoxyethylene sorbitan sesquipalmitate andpolyoxyethylene sorbitan sesquistearate, fatty acid esters such assaturated fatty acid methyl ester, unsaturated fatty acid methyl ester,saturated fatty acid butyl ester, unsaturated fatty acid butyl ester,saturated fatty acid stearyl esters, unsaturated fatty acid stearylesters, saturated fatty acid octyl esters, unsaturated fatty acid octylesters, stearic acid polyethylene glycol esters, oleic acid polyethyleneglycol esters and rosin polyethylene glycol esters, fatty acids such asstearic acid, oleic acid, palmitic acid, lauric acid and myristic acidand amide compounds of those fatty acids, higher fatty acidmonoethanolamides and higher fatty acid diethanolamides such as lauricacid monoethanolamide and coconut fatty acid diethanolamide, amidecompounds such as polyoxyethylene stearic amide, coconut diethanolamide(1-2 type/1-1 type) and alkylalkylolamide and alkanolamides.

Further, they include alkanolamines represented byR—(CH₂CH₂O)mH(CH₂CH₂O)nH and R—NH—C₃H₆—NH₂ (R is oleyl, octyl, dodecyl,tetradecyl, hexadecyl, octadecyl or the like or higher fatty acidobtained from coconut, beef tallow and soybean), primary aminesrepresented by R—NH₂ (R is oleyl, octyl, dodecyl, tetradecyl, hexadecyl,octadecyl or the like or higher fatty acid obtained from coconut, beeftallow and soybean), secondary amines represented by R1R2-NH(R1 and R2are oleyl, octyl, dodecyl, tetradecyl, hexadecyl, octadecyl or the likeor higher fatty acid obtained from coconut, beef tallow and soybean),tertiary amines represented by R1R2R3-N(R1, R2 and R3 are oleyl, octyl,dodecyl, tetradecyl, hexadecyl, octadecyl or the like or higher fattyacid obtained from coconut, beef tallow and soybean), various synthetichigher alcohols and various natural higher alcohols.

The anionic surfactants include, for example, carboxylic acid salts suchas specific fatty acid soaps and rosin soaps, salts of castor oilsulfuric acid ester, salts of alcohol sulfuric acid ester such as sodiumsalts of lauryl alcohol sulfuric acid ester, amine salts of laurylalcohol sulfuric acid ester, sodium salts of natural alcohol sulfuricacid esters and sodium salts of higher alcohol sulfuric acid esters,salts of sulfuric acid esters such as amine salts of lauryl alcoholether sulfuric acid ester, sodium salts of lauryl alcohol ether sulfuricacid ester, amine salts of synthetic higher alcohol ether sulfuric acidesters, sodium salts of synthetic higher alcohol ether sulfuric acidesters, amine salts of alkyl polyether sulfuric acid esters, sodiumsalts of alkyl polyether sulfuric acid esters, amine salts of naturalalcohol EO (ethylene oxide) adduct sulfuric acid esters, sodium salts ofnatural alcohol EO (ethylene oxide) adduct sulfuric acid esters, aminesalts of synthetic alcohol EO (ethylene oxide) adduct sulfuric acidesters, sodium salts of synthetic alcohol EO (ethylene oxide) adductsulfuric acid esters, amine salts of alkylphenol EO (ethylene oxide)adduct sulfuric acid esters, sodium salts of alkylphenol EO (ethyleneoxide) adduct sulfuric acid esters, amine salts of polyoxyethylenenonylphenyl ether sulfuric acid esters, sodium salts of polyoxyethylenenonylphenyl ether sulfuric acid esters, amine salts of polyoxyethylenepolycyclic phenyl ether sulfuric acid esters and sodium salts ofpolyoxyethylene polycyclic phenyl ether sulfuric acid esters, sulfonicacid salts such as various alkylaryl sulfonic acid amine salts, variousalkylaryl sulfonic acid sodium salts, naphthalenesulfonic acid aminesalts, naphthalenesulfonic acid sodium salts, variousalkylbenzenesulfonic acid amine salts, various alkylbenzenesulfonic acidsodium salts and naphthalenesulfonic acid condensation products, saltsof polyoxyalkylene base compound sulfonic acids such as amine salts ofpolyoxyalkylene nonylphenyl ether sulfonic acids, sodium salts ofpolyoxyethylene nonylphenyl ether sulfonic acids, amine salts ofpolyoxyethylene specific aryl ether sulfonic acids, sodium salts ofpolyoxyethylene specific aryl ether sulfonic acids, amine salts ofpolyoxyalkylene tridecylphenyl ether sulfonic acids, sodium salts ofpolyoxyethylene tridecylphenyl ether sulfonic acids, amine salts ofpolyoxyethylene alkyl ether sulfonic acids and sodium salts ofpolyoxyethylene alkyl ether sulfonic acids, salts of sulfosuccinic acidesters such as amine salts of dialkyl sulfosuccinates, sodium salts ofdialkyl sulfosuccinates, amine salts of polycyclic phenylpolyethoxysulfosuccinates, sodium salts of polycyclic phenylpolyethoxysulfosuccinates, amine salts of polyoxyalkylene alkyl ethersulfosuccinic acid monoesters and sodium salts of polyoxyalkylene alkylether sulfosuccinic acid monoesters, phosphoric acid esters such asalkylphosphoric acid esters, alkoxyalkylphosphoric acid esters, higheralcohol phosphoric acid esters, alkylphenol type phosphoric acid esters,aromatic phosphoric acid esters, polyoxyalkylene alkyl ether phosphoricacid esters and polyoxyalkylene alkylaryl ether phosphoric acid esters,and phosphoric acid salts.

The cationic surfactants include, for example, alkyltrimethylamine basequaternary ammonium salts represented by R—N(CH₃)₃X (R is stearyl,cetyl, lauryl, oleyl, dodecyl, coconut, soybean, beef tallow or thelike, and X is halogen, amine or the like), quaternary ammonium saltssuch as tetramethylamine base salts and tetrabutylamine base salts,acetic acid salts represented by (RNH₃) (CH₃COO) (R is stearyl, cetyl,lauryl, oleyl, dodecyl, coconut, soybean, beef tallow or the like),benzylamine base quaternary ammonium salts such aslauryldimethylbenzylammonium salts (halogen, amine salts and the like),stearyldimethylbenzylammonium salts (halogen, amine salts and the like)and dodecyldimethylbenzylammonium salts (halogen, amine salts and thelike) and polyoxyalkylene base quaternary ammonium salts represented byR(CH₃)N(C₂H₄O)mH(C₂H₄₀)nH.X (R is stearyl, cetyl, lauryl, oleyl,dodecyl, coconut, soybean, beef tallow or the like, and X is halogen,amine or the like).

The amphoteric surfactants include, for example, various betaine typesurfactants, various imidazoline type surfactants, β-alanine typesurfactants and polyoctylpolyaminoethylglycine hydrochloride.

In the present invention, the high molecular type surfactants which canbe used are polymers having a large molecular weight (number averagemolecular weight, hereinafter the same shall apply) instead of thosehaving a small molecular weight of several hundred, and they includecompounds including low molecular weight polymers having a molecularweight of 10000 or less which are usually called oligomers in additionto polymers having a molecular weight of about 10000 or more which areusually called macromolecules (polymers).

The following anionic high molecular type surfactants, cationic highmolecular type surfactants and nonionic high molecular type surfactantscan be given as the high molecular type surfactants.

The anionic high molecular type surfactants include, for example,styrene-maleic anhydride copolymers, olefin-maleic anhydride copolymers,naphthalenesulfonic acid salt condensation products, formalincondensation products of naphthalenesulfonic acid salts, poly(sodiumacrylate), polycarboxylic acid type anionic surfactants,polyacrylamide-partially hydrolyzed products, acrylamide-sodium acrylatecopolymers and sodium alginate.

The cationic high molecular type surfactants include, for example,polyethyleneimine, polyvinylimidazolidone, aminoalkyl(meth)acrylate-acrylamide copolymers, acrylamide Mannich denaturedproducts and chitosan.

The nonionic high molecular type surfactants include, for example,polyvinyl alcohol, copolymers of polyethylene ether ester,polyacrylamide, polycarboxylic acid base compounds, oligomers ofhydroxyfatty acids, denatured products of oligomer of hydroxyfattyacids, polyhydroxyfatty acids, polyhydroxyfatty acid-denatured products,poly-1,2-hydroxystearic acid, N-polyoxyalkylenepolyalkylenepolyamine andstarch.

In the dispersant of the present invention, particularly preferably usedare nonionic or anionic surfactants and nonionic or anionic highmolecular type surfactants which are less liable to exert an adverseeffect on positive or negative electrification of the particle surfaceand which are less liable to exert an adverse effect when encapsulatingthe liquid for electrophoretic display into microcapsules.

The above dispersants can be used alone or in combination of two or morekinds thereof. A content thereof is suitably determined according to thefine particles used and the kind of the solvent, and it is preferably0.01 to 50.0%, more preferably 1 to 30% based on the total amount of theliquid for electrophoretic display.

If a content of the dispersant is less than 0.01%, it becomes difficultto secure satisfactory dispersion stability of the dispersion system. Onthe other hand, if it exceeds 50.0%, conductivity of the dispersionliquid medium grows high, and a viscosity of the dispersion system israised, so that an adverse effect is exerted on the displaycharacteristics. Accordingly, both ranges are not preferred.

In the present invention, those of various types which have so far beenused for electrophoretic display can be used as the dispersion liquidmedium.

To be specific, they include aromatic hydrocarbons such as benzene,alkylbenzene derivatives such as toluene, xylene, ethylbenzene anddodecylbenzene, diarylalkane derivatives such as phenylxylylethane,1,1-ditolylethane, 1,2-ditolylethane and1,2-bis(3,4-dimethylphenylethane) (BDMF), alkylnaphthalene derivativessuch as diisopropylnaphthane, alkylbiphenyl derivatives such asmonoisopropylbiphenyl, isopropylbiphenyl and isoamylbiphenyl, terphenylderivatives which are hydrogenated in various proportions,triaryldimethane derivatives such as dibenzyltoluene, benzylnaphthalenederivatives, phenylene oxide derivatives, diarylalkylene derivatives,arylindane derivatives, polychlorinated biphenyl derivatives andnaphthene base hydrocarbons.

Further, they include aliphatic hydrocarbons such as hexane,cyclohexane, kerosene, isoper and paraffin base hydrocarbons,halogenated hydrocarbons such as chloroform, trichloroethylene,tetrachloroethylene, trifluoroethylene, tetrafluoroethylene,dichloromethane and ethyl bromide, phosphoric acid esters such astricresyl phosphate, trioctyl phosphate, octyldiphenyl phosphate andtricyclohexyl phosphate, phthalic acid esters such as dibutyl phthalate,dioctyl phthalate, dilauryl phthalate and dicyclohexyl phthalate,carboxylic acid esters such as butyl oleate, diethylene glycoldibenzoate, dioctyl sebacate, dibutyl sebacate, dibutyl adipate,trioctyl trimellitate, acetyltriethyl citrate, octyl maleate, dibutylmaleate and ethyl acetate, chlorinated paraffin andN,N-dibutyl-2-butoxy-5-tertiary octylaniline, but they shall not berestricted thereto.

Further, in the present invention, the dispersion liquid media can beused alone or in a mixture of two or more kinds thereof. Particularly, asolvent having a low dielectric constant (5.0 or lower) is preferablyused as the dispersion liquid medium, and it is preferably selected sothat it has the same specific gravity as those of the fine particles.

A content of the dispersion liquid media is suitably determinedaccording to the fine particles used and the kind of the dispersant, andit is preferably 25 to 85%, more preferably 30 to 60% based on the totalamount of the liquid for electrophoretic display.

If a content of the dispersion liquid medium is less than 25%, aviscosity of the liquid grows high, and the response speed is lowered.On the other hand, if it exceeds 85%, the satisfactory contrast can notbe displayed. Accordingly, both ranges are not preferred.

Further, in the present invention, the dispersion liquid media describedabove which are colored by dissolving therein various oil-soluble dyescan be used. In this case, the following ones can be given as the dyeswhich can be used, but the present invention shall not be restricted tothem.

The dyes which can be used include, for example, spirit black (SS, SSBB,AB), nigrosine bases (SA, SAP, SAPL, EE, EEL, EX, EXBP, EB), oil yellow(105, 107, 129, 3G, GGS), oil orange (201, PS, PR), fast orange, oil red(5B, PR, OG), oil scarlet, oil pink 312, oil violet #730, macrorex blueRR, Sumiplast Green G, oil brown (GR, 416), Sudan Black X60, oil green(502, BG), oil blue (613, 2N, BOS), oil black (HBE, 860, BS), ValifastYellow (1101, 1105, 3108, 4120), Valifast Orange (3209, 3210), ValifastRed (1306, 1355, 2303, 3304, 3306, 3320), Valifast Pink 2310N, ValifastBrown (2402, 3405), Valifast Blue (3405, 1501, 1603, 1605, 1607, 2606,2610), Valifast Violet (1701, 1702) and Valifast Black (1802, 1807,3804, 3810, 3820, 3830) as representative ones.

The above dyes are preferably used by selecting the colors which candisplay the contrast against the fine particles used, and two or morekinds thereof can be used to control the color.

The liquid for electrophoretic display according to the first inventioncomprises at least the alkylpolyetheramine having the structural unitrepresented by Formula (I) described above, one or more kinds of thefine particles described above, the dispersant and the dispersion liquidmedium, wherein the fine particles contain fine particles subjected tosurface treatment for making lipophilic, and it can contain the suitableamounts of optional components used for a liquid for electrophoreticdisplay as long as the effects of the present invention are not damaged.

The optional components which can be used include UV absorbers,antioxidants, light stabilizers, heat stabilizers and fungicides.

The liquid for electrophoretic display according to the first inventioncan be prepared by mixing and stirring at least the alkylpolyetheraminehaving the structural unit represented by Formula (I) described above,one or more kinds of the fine particles described above containing thefine particles subjected to surface treatment for making lipophilic, thedispersant and the dispersion liquid medium and then subjecting themixture to various dispersion treatment by a medialess dispersion methodsuch as supersonic dispersion and a dispersion method using media of awet bead mill. Further, classification treatment making use of aprinciple of centrifugal separation and a particle size-controlling by afiltration method can be carried out, if necessary, in order to controla particle size of the fine particles.

In the liquid for electrophoretic display thus constituted according tothe first invention, used is the liquid which comprises at least thealkylpolyetheramine having the structural unit represented by Formula(I) described above, one or more kinds of the fine particles, thedispersant and the dispersion liquid medium and in which the particlescontaining the fine particles subjected to surface treatment for makinglipophilic are used for the fine particles described above, whereby theliquid which has a high contrast on a display face and can display acontrast with a high reliability even in repetitive display and which isexcellent in a response can be provided.

The liquid for electrophoretic display according to the second inventioncomprises at least the alkylpolyetheramine having the structural unitrepresented by Formula (I) described above, the polyoxyethyleneoxypropylene block polymer having the structural unit represented byFormula (II) described above, one or more kinds of the fine particlesand the dispersion liquid medium:OH(C₂H₄O)p(C₃H₆O)qH  (II)in Formula (II) described above, p and q are positive numbers.

The polyoxyethylene oxypropylene block polymer used in the secondinvention improves dispersibility of the fine particles and agingstability of the liquid for electrophoretic display, and it may be anyone as long as it has the structure represented by Formula (II)described above. The polyoxyethylene oxypropylene block polymer havingan average molecular weight of 1000 to 4000 is preferred from theviewpoint of solubility in a solvent having a low dielectric constant.The polyoxyethylene oxypropylene block polymer having an ethylene oxideamount of 50% by weight or less is more preferred, and thepolyoxyethylene oxypropylene block polymer having an ethylene oxideamount of 5 to 30% by weight is particularly preferred.

The polyoxyethylene oxypropylene block polymer which can specifically beused includes at least one kind (one kind or two or more kinds) ofPronon 102 (average molecular weight: 1250, ethylene oxide amount: 20%by weight), Pronon 104 (average molecular weight: 1670, ethylene oxideamount: 40% by weight), Pronon 201 (average molecular weight: 2220,ethylene oxide amount: 10% by weight), Pronon 204 (average molecularweight: 3300, ethylene oxide amount: 40% by weight) and Pronon 208(average molecular weight: 10000, ethylene oxide amount: 80% by weight)each manufactured by NOF Corporation. However, it shall not berestricted to them as long as it is dissolved in the dispersion medium.

A content of the polyoxyethylene oxypropylene block polymers ispreferably 0.01 to 30%, more preferably 0.01 to 10% based on the totalamount of the display liquid.

If a content of the polyoxyethylene oxypropylene block polymers is lessthan 0.01%, the fine particles are reduced in dispersibility, and theliquid for electrophoretic display is deteriorated in aging stability.On the other hand, if it exceeds 30%, an adverse effect is exerted onthe display performances such as the contrast. Accordingly, both rangesare not preferred.

In the liquid for electrophoretic display according to the secondinvention, the polyoxyethylene oxypropylene block polymer having thecharacteristics described above is used in comparison with the liquidfor electrophoretic display according to the first invention describedabove, so that one or more kinds of the fine particles which are notsubjected to the surface treatment for making lipophilic can be used aswell. Further, the effects of the present invention can be exhibitedwithout using the dispersant.

The respective components such as the alkylpolyetheramine having thestructural unit represented by Formula (I) described above, one or morekinds of the fine particles, the dispersion liquid medium, thedispersant, the surfactant, the high molecular type surfactant and thecolorant (dye) excluding the polyoxyethylene oxypropylene block polymerhaving the characteristics described above which is used for the liquidfor electrophoretic display according to the second invention and therespective contents thereof are the same as the respective componentsand the contents thereof used for the liquid for electrophoretic displayaccording to the first invention described above, and therefore theexplanations thereof shall be omitted. In the second invention, the fineparticles subjected to the surface treatment for making lipophilic maybe used as the preferred embodiment, and the dispersant may be added.

The liquid for electrophoretic display according to the second inventioncomprises at least the alkylpolyetheramine having the structural unitrepresented by Formula (I) described above, the polyoxyethyleneoxypropylene block polymer having the structural unit represented byFormula (II) described above, one or more kinds of the fine particlesand the dispersion liquid medium, and it may contain the suitableamounts of optional components used for a liquid for electrophoreticdisplay as long as the effects of the present invention are not damaged.

The optional components which can be used include UV absorbers,antioxidants, light stabilizers, heat stabilizers and fungicides.

The liquid for electrophoretic display according to the second inventioncan be prepared by mixing and stirring at least the alkylpolyetheraminehaving the structural unit represented by Formula (I) described above,the polyoxyethylene oxypropylene block polymer having the structuralunit represented by Formula (II) described above, one or more kinds ofthe fine particles and the dispersion liquid medium and then subjectingthe mixture to various dispersion treatment by a medialess dispersionmethod such as supersonic dispersion and a dispersion method using amedia of a wet bead mill. Further, classification treatment making useof a principle of centrifugal separation and particle size-controllingby a filtration method may be carried out, if necessary, in order tocontrol a particle size of the fine particles.

In the liquid for electrophoretic display thus constituted according tothe second invention, used is the liquid comprising at least thealkylpolyetheramine having the structural unit represented by Formula(I) described above, the polyoxyethylene oxypropylene block polymerhaving the structural unit represented by Formula (II) described above,one or more kinds of the fine particles and the dispersion liquidmedium, whereby the liquid which displays a high contrast on a displayface and can display the contrast with high reliability even inrepetitive display and which is excellent in a response can be provided.

The liquid for electrophoretic display according to the third inventionis characterized by comprising at least the alkylpolyetheramine havingthe structural unit represented by Formula (I) described above, thepolyoxyethylene oxypropylene block polymer having the structural unitrepresented by Formula (II) described above, the acetylene derivativehaving the structural unit represented by the following Formula (III),one or more kinds of the fine particles and the dispersion liquidmedium:

in Formula (III) described above, R₄ and R₅ are a saturated hydrocarbongroup or an unsaturated hydrocarbon group; R₆ is OCH₂CH(CH₃)— or(OCH₂CH₂)m-OH; R₇ is OCH₂CH(CH₃)— or (OCH₂CH₂)n-OH; m and n are positivenumbers; m and n are 0 or a positive number; and R₆ and R₇ may be thesame or different.

The acetylene derivative used in the third invention improves durabilityand reliability of the liquid for electrophoretic display, and it may beany one as long as it has the structure represented by Formula (III)described above. It includes, for example, acetylene glycol derivatives(R₄ and R₅ are an isobutyl group, and R₆ and R₇ are a —OH group (m and nare 0)), ethylene oxide adducts of acetylene glycol derivatives (R₄ andR₅ are an isobutyl group; R₆ is (OCH₂CH₂)m-OH; R₇ is (OCH₂CH₂)n-OH; mand n are positive numbers), propylene oxide adducts of acetylene glycolderivatives (R₄ and R₅ are an isobutyl group, and R₆ and R₇ areOCH₂CH(CH₃)—) and mixtures of the derivatives and organic solvents(ethylene glycol, dipropylene glycol monomethyl ether and the like).They can be used alone (one kind) or in a mixture of two or more kindsthereof.

To be specific (including cases in which they are used in examplesdescribed later), capable of being given are commercially availableSurfynol 104 (acetylene glycol derivative; R₄ and R₅ are an isobutylgroup; R₆ and R₇ are a —OH group (m and n are 0); and HLB is 4),Surfynol 104E (mixture of Surfynol 104 (50% by weight) and ethyleneglycol (50% by weight), HLB: 4), Surfynol 104DPM (mixture of Surfynol104 (50% by weight) and dipropylene glycol monomethyl ether (50% byweight), HLB: 4), Surfynol 420 (ethylene oxide (20% by weight) adduct ofSurfynol 104, HLB: 4), Surfynol DF-110D (acetylene diol, HLB: 4) andOlfin B (acetylene alcohol, HLB: 10 or less) (all manufactured by NissinChemical Industry Co., Ltd.).

Preferred is the acetylene derivative represented by Formula (III)described above in which HLB is preferably 10 or less, more preferably 2to 5. Use of the acetylene derivative having HLB of 10 or less furtherenhances the affinity of the fine particles to the liquid forelectrophoretic display and makes the repetitive display characteristicsbetter.

When using acetylene derivatives which are not included in thoserepresented by Formula (III) described above, the affinity to the liquidfor electrophoretic display runs short, and the satisfactory effect ofimproving the repetitive display characteristics is not exhibited.Accordingly, they are not preferred.

A content of the above acetylene derivatives is preferably 0.01 to 10%,more preferably 0.05 to 5.0% based on the total amount of the displayliquid.

If a content of the acetylene derivatives is less than 0.01%, thesatisfactory effect of improving the repetitive display characteristicsis not exhibited. On the other hand, if it exceeds 10%, a rise in aviscosity of the liquid for electrophoretic display is brought about,and an adverse effect is exerted on the electrophoretic characteristicsin a certain case.

The liquid for electrophoretic display according to the third inventionfurther comprises the acetylene derivative having the characteristicsdescribed above in comparison with the liquid for electrophoreticdisplay according to the second invention.

The respective components such as the alkylpolyetheramine having thestructural unit represented by Formula (I) described above, thepolyoxyethylene oxypropylene block polymer having the structural unitrepresented by Formula (II) described above, one or more kinds of thefine particles, the dispersion liquid medium, the dispersant, thesurfactant, the high molecular type surfactant and the colorant (dye)excluding the acetylene derivative having the characteristics describedabove which is used for the liquid for electrophoretic display accordingto the third invention and the respective contents thereof are the sameas the respective components and the contents thereof used for theliquids for electrophoretic display according to the first invention andthe second invention each described above, and therefore theexplanations thereof shall be omitted. Also in the third invention, thefine particles which are subjected to the surface treatment for makinglipophilic may be used as the preferred embodiment, and the dispersantmay be added.

The liquid for electrophoretic display according to the third inventioncomprises at least the alkylpolyetheramine having the structural unitrepresented by Formula (I) described above, the polyoxyethyleneoxypropylene block polymer having the structural unit represented byFormula (II) described above, the acetylene derivative having thestructural unit represented by Formula (III) described above, one ormore kinds of the fine particles and the dispersion liquid medium, andit may contain the suitable amounts of optional components used for aliquid for electrophoretic display as long as the effects of the presentinvention are not damaged.

The optional components which can be used include UV absorbers,antioxidants, light stabilizers, heat stabilizers and fungicides.

The liquid for electrophoretic display according to the third inventioncan be prepared by mixing and stirring at least the alkylpolyetheraminehaving the structural unit represented by Formula (I) described above,the polyoxyethylene oxypropylene block polymer having the structuralunit represented by Formula (II) described above, the acetylenederivative having the structural unit represented by Formula (III)described above, one or more kinds of the fine particles and thedispersion liquid medium and then subjecting the mixture to variousdispersion treatment by a medialess dispersion method such as supersonicdispersion and a dispersion method using a media of a wet bead mill.Further, classification treatment making use of a principle ofcentrifugal separation and particle size-controlling by a filtrationmethod can be carried out, if necessary, in order to control a particlesize of the fine particles.

In the liquid for electrophoretic display thus constituted according tothe third invention, used is the liquid comprising at least thealkylpolyetheramine having the structural unit represented by Formula(I) described above, the polyoxyethylene oxypropylene block polymerhaving the structural unit represented by Formula (II) described above,the acetylene derivative having the structural unit represented byFormula (III) described above, one or more kinds of the fine particlesand the dispersion liquid medium, whereby the liquid which displays ahigh contrast on a display face and can display the contrast with highreliability even in repetitive display and which is excellent in aresponse can be provided.

Next, the medium for electrophoretic display according to the presentinvention is characterized by that any one of the liquids forelectrophoretic display prepared in the first invention to the thirdinvention is encapsulated into each independent structures ofmicrocapsules or cells.

FIG. 2 and FIG. 3 are the embodiments of using a liquid of a singleparticle type or a double particle type in which the liquid forelectrophoretic display is encapsulated into a structure comprisingmicrocapsules.

In FIG. 2, a liquid for electrophoretic display prepared by dispersing aprescribed amount of titanium oxide particles or titanium oxideparticles subjected to treatment for making lipophilic in a solutioncolored to black with an oil-soluble dye is micro-encapsulated by aurea-formaldehyde resin, wherein an illustrated symbol 1 is a positivelyelectrified (titanium oxide) white particle; 2 is a black solvent; and 3is a capsule wall.

In FIG. 3, a liquid for electrophoretic display prepared by dispersingthe prescribed amounts of titanium oxide particles or titanium oxideparticles subjected to treatment for making lipophilic and cross-linkedacryl base polymer particles including carbon black in a dispersionmedium is micro-encapsulated by a urea-formaldehyde resin, wherein anillustrated symbol 4 is a positively electrified (titanium oxide) whiteparticle; 5 is a non-electrified black particle (cross-linked acryl basepolymer particle including carbon black); 6 is a non-colored solvent;and 7 is a capsule wall.

FIG. 4 to FIG. 6 are the respective embodiments in which the liquid forelectrophoretic display is filled into a structure comprising a cell,and the respective patterns of the cells are schematically shown.Further, FIG. 7 to FIG. 9 each schematically show cross-sectionaldrawings in a case where a microcapsule and a cell structure sheet arearranged between counter electrodes, wherein in FIG. 7 to FIG. 9, anillustrated symbol 10 is a transparent electrode; 11 is a binder resinlayer; 12 is a microcapsule; 13 is a counter substrate; and 14 is acell-forming sheet (the same shall apply to FIG. 10 and FIG. 11).

The microcapsule used for the medium for electrophoretic displayaccording to the present invention can be prepared by an in-situpolymerization method, an interfacial polymerization method and acoacervation method which are usually used. In this case, a wallmaterial for the microcapsule includes polyurethanes, polyureas,polyurea-polyurethanes, urea-formaldehyde resins, melamine-formaldehyderesins, polyamides, polyesters, polysulfoneamides, polycarbonates,polysulfinates, epoxy resins, acrylic acid ester resins, methacrylicacid ester resins, vinyl acetate resins and gelatin.

Further, the microcapsules used for the display particles forelectrophoretic display according to the present invention havepreferably a particle size of 10 to 200 μm.

If a particle size of the microcapsules is less than 10 μm, theinconvenience that the contrast is not sufficiently obtained is involvedtherein. On the other hand, if it exceeds 200 μm, the inconvenience thatthe satisfactory response speed is not obtained without raising theapplied voltage. Accordingly, both ranges are not preferred.

A particle size of the microcapsules falls preferably in certaindistribution as much as possible. If it is not uniform, uneven displayis caused, and the display characteristics are lowered.

The microcapsules used for the medium for electrophoretic displayaccording to the present invention have preferably flexibility so thatthe microcapsules are arranged in a high density in order to preventgaps from being generated therebetween when installing them between thecounter electrodes disposed in the display device.

This reduces very much a proportion of a region which does notcontribute to display, and the contrast grows sharp. Further, themicrocapsules are brought into face contact with the counter electrode,and the uneven display is less liable to be generated, so that theelectrophoretic display device having a display characteristic of highquality is obtained.

The microcapsule having flexibility results in being increased inmechanical strength and improved as well in characteristics whenarranging the microcapsules on the electrodes for display by a coatingmethod.

A water dispersion type resin base binder and a solvent dissolving typeresin base binder can be used for a coating liquid for coating themicrocapsules used for the medium for electrophoretic display accordingto the present invention on the substrate electrode. It is preferablethat dispersibility of the microcapsules in the coating liquid is goodin order to evenly arrange the microcapsules when coating them on thesubstrate.

Further, the microcapsules are preferably brought into even contact witheach other at a drying step, and the microcapsules are preferably notinhibited from being brought into face contact with each other at afinal drying step.

In the medium for electrophoretic display according to the presentinvention in which the liquid for electrophoretic display is filled intothe structure comprising the independent and divided cell as shown inFIG. 4 to FIG. 6, an electrode part and a cell part which are broughtinto contact with the liquid for electrophoretic display in thestructure of the cell filled with the liquid for electrophoretic displayare preferably subjected to hydrophilization treatment selected fromozone treatment, plasma treatment, corona treatment, UV itoro treatment,sputtering treatment, polymer layer-forming treatment, inorganiclayer-forming treatment and organic or inorganic hybrid layer-formingtreatment from the viewpoint of controlling an affinity with theelectrophoretic particles in the liquid.

In the ozone treatment, the surface of a cell sheet is exposed to ozoneto be brought into contact with ozone molecules for the purpose ofintroducing a functional group (hydrophilic group) such as ahydroxyperoxy group, a hydroxyl group and a carbonyl group, whereby thehydrophilization treatment is carried out. The exposing method includesa method in which it is held in atmosphere in which ozone is present forprescribed time and a method in which it is exposed in ozone flow forprescribed time, but it shall not specifically be restricted.

The plasma treatment is carried out by putting the cell sheet describedabove in a vessel containing air, oxygen, nitrogen, carbon dioxide,argon and neon to expose to plasma produced by glow discharge, and ithas the purpose of introducing a functional group (hydrophilic group)such as a carboxylic acid group, a carbonyl group and an amino groupeach containing oxygen or nitrogen into a cell sheet surface part. Adischarge system for generating plasma includes direct currentdischarge, low frequency discharge, radiofrequency wave discharge andmicrowave discharge, but it shall not specifically be restricted tothem. Air plasma treatment and oxygen plasma treatment are preferredfrom the viewpoint of introducing a hydrophilic functional groupcontaining an oxygen atom.

In the corona treatment, the cell sheet described above is allowed topass in an electric field in which corona discharge is generated,whereby an inside surface part of the cell sheet can be subjected tohydrophilization treatment.

In the UV itoro treatment, carried out is treatment (silicificationflame treatment, titanium oxidation flame treatment and aluminumoxidation flame treatment) in which blown onto the cell sheet describedabove is flame of fuel gas containing at least one modifier compoundselected from the group consisting of alkylsilane compounds,alkoxysilane compounds, alkyltitanium compounds, alkoxytitaniumcompounds, alkylaluminum compounds and alkoxyaluminum compounds,preferably at least one of modifier compounds having a boiling point of10 to 100° C., whereby an inside surface part of the cell sheet can besubjected to hydrophilization treatment. A flame temperature in carryingout the blowing treatment is 500 to 1500° C., and the treating time is0.1 to 100 seconds.

Further, the electrode part and the cell part which are brought intocontact with the liquid for electrophoretic display can be subjected aswell to hydrophilization treatment by sputtering treatment, polymerlayer-forming treatment, inorganic layer-forming treatment and organicor inorganic hybrid layer-forming treatment.

In the medium for electrophoretic display according to the presentinvention, a volume of the independent and divided cell is preferably1×10⁻⁹ to 1×10⁻³ ml in the medium in which the structure comprising theindependent and divided cell is filled, as shown in FIG. 4 to FIG. 6,with the liquid for electrophoretic display.

If this volume is less than 1×10⁻⁹ ml, deterioration in the displaycontrast is liable to be brought about. On the other hand, if it exceeds1×10⁻³ ml, coagulation is liable to be caused in an inside of the cellsto bring about failures such as uneven display.

Also, in the medium for electrophoretic display in which the liquid forelectrophoretic display thus constituted according to the presentinvention is encapsulated into microcapsules or cells, the contrast onthe display face is sharp, and the contrast can be displayed with highreliability even in repetitive display. In addition, the characteristicsin which a response is excellent are realized.

Further, the electrophoretic device of the present invention ischaracterized by having a pair of substrates on at least one of whichelectrodes having a light transmitting property are formed and themedium for electrophoretic display having the structure described abovebetween the substrates.

The electrophoretic display device of the present invention includes,for example, devices having the following forms of a) to f), but itshall not be restricted to them.

a) An electrophoretic display device in which a pair of base materialsfor display equipped with an electrode on one face of a substrate arearranged via spacers so that the electrode faces are oppositely disposedto form a space and in which the liquid for electrophoretic displayaccording to the present invention is filled into the space and at leastone of the base materials for display is a transparent substrateprovided on one face thereof with a transparent electrode.

b) An electrophoretic display device in which an insulating film and abase material for display equipped with an electrode on one face of asubstrate are oppositely disposed to via spacers to form a space and inwhich the liquid for electrophoretic display according to the presentinvention is filled into the space and at least one of the base materialfor display and the insulating film is transparent.

c) An electrophoretic display device in which a pair of base materialsfor display equipped with an electrode on one face of a substrate arearranged via spacers so that the electrode faces are oppositely disposedto form a space and in which the display particles for electrophoreticdisplay according to the present invention are filled into the space andat least one of the base materials for display is a transparentsubstrate provided on one face thereof with a transparent electrode.

d) An electrophoretic display device in which an insulating film and abase material for display equipped with an electrode on one face of asubstrate are oppositely disposed via spacers to form a space and inwhich the display particles for electrophoretic display according to thepresent invention are filled into the space and at least one of the basematerial for display and the insulating film is transparent.

e) An electrophoretic display device in which the medium forelectrophoretic display according to the present invention is coatedtogether with a binder on a base material for display equipped with atransparent or opaque electrode on one face of a transparent or opaquesubstrate.

f) An electrophoretic display device in which a pair of base materialsfor display equipped with an electrode on one face of a substrate arearranged via spacers so that the electrode faces are oppositely disposedto form a space and in which the liquid for electrophoretic displayaccording to the present invention is filled into the space divided intoindependent cells by lattice-shaped walls and at least one of the basematerials for display is a transparent substrate provided on one facethereof with a transparent electrode.

In this display device, the independent and divided cell has preferablya volume of 1×10⁻⁹ to 1×10⁻³ ml.

FIG. 10 is an electrophoretic display device using a display medium inwhich the liquid for electrophoretic display of the single particle typeshown in FIG. 2 is encapsulated into a structure comprisingmicrocapsules, and FIG. 11 is an electrophoretic display device using adisplay medium in which the liquid for electrophoretic display of thedouble particle type shown in FIG. 3 is encapsulated into a structurecomprising microcapsules.

In FIG. 12, shown is a schematic drawing of an electrophoretic displaydevice in a case in which ITO glass electrodes having a thickness (D1,D3) of 1100 μm are used as counter electrodes and a sheet of a spacerhaving a thickness (D2) of 500 μm is used to apply voltage, and d1 andd2 are a thickness (0.15 μm) of an ITO thin film.

Also, in addition to the microcapsule type described above, afilm-shaped sheet having a lot of cells filled with the liquid forelectrophoretic display may be interposed between counter electrodes inthe electrophoretic display device in the present invention.

In respect to a forming method of the sheet for receiving the liquid forelectrophoretic display, it can be prepared by forming fine cells on athin film sheet by applying various UV laser processing techniques or bya photoetching method and various printing methods.

The electrophoretic display device thus constituted according to thepresent invention has a high contrast and can display the contrast withhigh reliability even in repetitive display, and the characteristics inwhich a response is excellent are realized.

EXAMPLES

Next, the present invention shall be explained in detail with referenceto examples and comparative examples, but the present invention shallnot be restricted to the following.

Examples 1 to 19 and Comparative Examples 1 to 6

Preparation of Liquids for Electrophoretic Display, the First Invention

Blend compositions of the respective examples and comparative examplesshown in the following Table 1 were dispersed for 60 minutes by means ofa paint shaker using glass beads to prepare liquids for electrophoreticdisplay.

Used were fine particles (A-1 to A-8 and B-1 to B-2), dyes, dispersionliquid media (C-1 to C-3), dispersants (D-1 to D-4) andalkylpolyetheramines (E-1 to E-6) each shown below.

Fine Particles A:

A-1: ITT-2 TiO₂ CR-50 (manufactured by Nikko Chemicals Co., Ltd.),titanium oxide treated the surface with a titan coupling agent, meanparticle size: about 0.4 μm

A-2: ITT-7 TiO₂ TTO-S-3 (manufactured by Nikko Chemicals Co., Ltd.),fine particle titanium oxide treated the surface with a titan couplingagent, mean particle size: 0.05 to 0.1 μm

A-3: KR-380 (manufactured by Titan Kogyo Co., Ltd.), titanium oxidetreated the surface with a lipophilic surface treating agent, meanparticle size: about 0.5 μm

A-4: KR-270 (manufactured by Titan Kogyo Co., Ltd.), titanium oxidetreated the surface with a lipophilic surface treating agent, meanparticle size: about 0.4 μm

A-5: Technopolymer MBX-20 White (manufactured by Sekisui Plastics Co.,Ltd.), PMMA colored fine particles, mean particle size: about 20 μm

A-6: Tipaque CR-50 (manufactured by Ishihara Sangyo Kaisha, Ltd.),titanium oxide having a hydrophilic surface, mean particle size: about0.4 μm

A-7: particles (mean particle size: about 0.4 μm) prepared by treatingTipaque CR-50 (manufactured by Ishihara Sangyo Kaisha, Ltd.) withPlenact AL-M (manufactured by Ajinomoto Co., Inc.)

A-8: particles (mean particle size: about 0.4 μm) prepared by treatingTipaque CR-50 (manufactured by Ishihara Sangyo Kaisha, Ltd.) withKBE-503 (silane base coupling agent, manufactured by Shin-Etsu ChemicalCo., Ltd.)

Fine Particles B:

B-1: Rubcouleur 220(MD) Black (acryl copolymer colored beads,manufactured by Dainichiseika Color & Chemicals MFG. Co., Ltd.), meanparticle size: about 10 μm

B-2: ITT-2 BLACK BL-100 (manufactured by Nikko Chemicals Co., Ltd.),black iron oxide treated the surface with a titan coupling agent, meanparticle size: about 0.25 μm Colorant (dye):

Oil Blue N (dye, manufactured by Wako Pure Chemical Industries, Ltd.)

Dispersion Liquid Medium C:

C-1: xylene

C-2: normal paraffin H (manufactured by Nippon Petrochemicals Co., Ltd.)

C-3: Nisseki Isosol H (manufactured by Nippon Petrochemicals Co., Ltd.)

Dispersant D:

D-1: sorbitan monooleate

D-2: sorbitan trioleate

D-3: NIKKOL DDP-2 (manufactured by Nikko Chemicals Co., Ltd., anionicsurfactant)

D-4: oleic acid

Alkylpolyetheramine E:

E-1: Nymeen L-201 (manufactured by NOF Corporation),hydroxyethyllaurylamine

E-2: Nymeen L-202 (manufactured by NOF Corporation), polyethylene glycollaurylamine

E-3: Nymeen S-202 (manufactured by NOF Corporation), polyethylene glycolstearylamine

E-4: Nymeen T₂-202 (manufactured by NOF Corporation), polyethyleneglycol alkyl(beef tallow)amine

E-5: Nymeen DT-203 (manufactured by NOF Corporation), polyoxyethylenealkyl(beef tallow)propylenediamine

E-6: trioctylamine TABLE 1 (blend unit: % by weight, total amount: 100)Fine particle Fine Fine Dispersion liquid Dispersant Alkylpoly- particleA particle B Colorant medium C D etheramine E Example 1 A-1 10 — 0.1 C-181.9 — D-1 4 E-1 4 Example 2 A-1 10 B-1 5 — C-3 77.0 — D-2 3 E-3 5Example 3 A-1 10 B-1 5 — C-3 77.0 — D-2 3 E-1 5 Example 4 A-1 10 B-1 5 —C-3 78.0 — D-2 3 E-2 4 Example 5 A-1 10 B-1 5 — C-3 78.0 — D-2 3 E-4 4Example 6 A-1 10 B-1 5 — C-1 34.85 — D-4 50 E-4 0.15 Example 7 A-1 7 B-15 — C-1 54.7 — D-4 30 E-4 0.3 Example 8 A-1 10 B-1 5 — C-1 73.0 — D-1 10E-3 2 Example 9 A-1 10 B-1 5 — C-1 37.5 C-3 37.5 D-2 5 E-3 5 Example 10A-1 10 B-1 5 — C-1 36.0 C-3 36.0 D-2 3 E-1 10 Example 11 A-1 10 B-1 5 —C-1 69.99 — D-2 0.01 E-1 20 Example 12 A-1 10 B-1 5 — C-3 76.0 — D-3 5E-3 4 Example 13 A-3 10 B-1 5 — C-3 77.0 — D-2 3 E-3 5 Example 14 A-4 10B-1 5 — C-3 77.0 — D-2 3 E-3 5 Example 15 A-7 10 B-1 5 — C-3 77.0 — D-23 E-3 5 Example 16 A-8 10 B-1 5 — C-3 77.0 — D-2 3 E-3 5 Example 17 A-510 B-1 4 — C-3 78.0 — D-2 3 E-3 5 Example 18 A-2 10 B-1 2 — C-3 78.0 —D-2 3 E-3 5 Example 19 A-5 10 B-2 2 — C-3 78.0 — D-2 3 E-3 5 ComparativeA-1 10 — 0.1 C-1 84.9 — D-1 5 — Example 1 Comparative A-1 10 B-1 5 — C-384.9 — — E-3 0.1 Example 2 Comparative A-1 10 B-1 5 — C-1 40.0 C-3 40.0D-2 5 — Example 3 Comparative A-6 10 B-1 5 — C-3 77.0 — D-2 3 E-1 5Example 4 Comparative A-1 10 B-1 5 — C-3 75.0 — D-2 3 E-5 5 Example 5Comparative A-1 10 B-1 5 — C-3 77.0 — D-2 3 E-6 5 Example 6

The respective liquids for electrophoretic display obtained according tothe formulations shown in Table 1 described above were used to preparemedia for electrophoretic display by methods described below, andevaluation of a reflectance on the white display face, visual evaluationof the white display face, evaluation of a reflectance on the coloreddisplay face, visual evaluation of the colored display face, evaluationof coagulation and adhesion of the fine particles and evaluation of theresponse and the contrast were carried out by the following respectiveevaluation methods.

The results obtained by evaluating the physical properties of the abovemedia for electrophoretic display are shown in the following Table 2.

Preparation of Media for Electrophoretic Display Using the Liquids forElectrophoretic Display:

Glass substrates (thickness: 1.1 mm) in which a transparent conductivefilm (ITO film) was formed in a thickness of 0.15 μm on one surface wereused as a substrate in which an electrode was provided on one surface,and a pair of the glass substrates were oppositely disposed via spacersof about 500 μm to form a cell.

The liquids for electrophoretic display prepared according to theformulations shown in Table 1 described above were filled into the abovespace to thereby prepare media for electrophoretic display.

Evaluation of Physical Properties of Media for Electrophoretic:

The respective media for electrophoretic display prepared in theexamples and the comparative examples by the method described above wereelectrophoresed by applying a voltage of +200 V or −200 V to theelectrodes of the medium to measure a reflectance on a white or coloreddisplay face formed by means of MSC-5N (manufactured by Suga TestInstruments Co., Ltd., hereinafter the same shall apply).

Further, visual evaluation of white display and colored display,evaluation of coagulation and adhesion state of the particles andevaluation of a contrast ratio were carried out by the followingmethods.

Visual Evaluation of White Display and Colored Display:

Whiteness of the white display face and a color density of the coloreddisplay face which were displayed by applying voltage were sensorilyevaluated according to the following evaluation criteria.

Visual evaluation criteria of the white display face:

◯: white

Δ: a little colored

X: strongly colored

Visual Evaluation Criteria of the Colored Display Face:

◯: fine and strongly colored

Δ: a little whitish

X: whitish

Evaluation of Coagulation and Adhesion State of Particles and Response:

Coagulation of the particles and an adhesion state thereof onto theelectrode surface were evaluated according to the following evaluationcriteria by visually observing a change and a state of a color tone ofthe displayed part when applying hundred times a voltage of +200 V or−200 V alternately at an interval of one second to switch over thedisplay.

Further, a response of a display change corresponding to switching overof the voltage was evaluated according to the following evaluationcriteria.

Evaluation Criteria of Coagulation and Adhesion State of Particles:

◯: little coagulation and adhesion

Δ: coagulation and adhesion are a little observed

X: coagulation and adhesion are caused

Evaluation Criteria of Response:

◯: quickly changed

Δ: reaction is a little delayed

X: reaction is delayed

Evaluation of Contrast Ratio:

A voltage of +200 V or −200 V was applied to set one visible displaypart to white display, and a focus was concentrated onto an outermostside display face thereof to measure white color reflection by 45°irradiation—vertical light reception. Then, a voltage of −200 V or +200V which was reverse to the first polarity was applied to change thevisible display part to colored display, and a reflectance on thecolored display face was measured in the same manner. The contrast ratiowas calculated from a ratio thereof (reflectance of the white displayface/reflectance of the colored display face). TABLE 2 Total evaluationReflectance Visual evaluation Reflectance Visual evaluation Coagulationand on white of white display on colored of colored adhesion of displayface face display face display face fine particles Response ContrastExample 1 35 ◯ to Δ 8 ◯ to Δ ◯ ◯ 4.4 Example 2 53 ◯ 5 ◯ ◯ ◯ 8.8 Example3 53 ◯ 6 ◯ ◯ ◯ 8.8 Example 4 51 ◯ 5 ◯ ◯ ◯ 10.2 Example 5 50 ◯ 6 ◯ ◯ ◯8.3 Example 6 51 ◯ 7 ◯ ◯ ◯ to Δ 7.3 Example 7 54 ◯ 7 ◯ ◯ ◯ to Δ 7.7Example 8 53 ◯ 6 ◯ ◯ ◯ to Δ 8.8 Example 9 54 ◯ 7 ◯ ◯ ◯ 7.7 Example 10 53◯ 6 ◯ ◯ ◯ 8.8 Example 11 47 ◯ 7 ◯ ◯ ◯ to Δ 8.7 Example 12 52 ◯ 7 ◯ ◯ ◯7.4 Example 13 52 ◯ 6 ◯ ◯ ◯ 8.7 Example 14 50 ◯ 6 ◯ ◯ ◯ 8.3 Example 1551 ◯ 7 ◯ ◯ ◯ 7.3 Example 16 52 ◯ 7 ◯ ◯ ◯ 7.4 Example 17 42 ◯ 7 ◯ ◯ ◯ 6.0Example 18 35 ◯ 8 ◯ ◯ ◯ 4.4 Example 19 35 ◯ 11 ◯ ◯ ◯ 3.8 Comparative 35Δ 8 X Δ Δ 4.4 Example 1 Comparative 30 Δ 13 Δ Δ Δ 2.3 Example 2Comparative 32 Δ 8 Δ Δ Δ 0.6 Example 3 Comparative the particles weredispersed but immediately coagulated, so that evaluation was impossibleExample 4 Comparative 20 Δ 16 Δ Δ X 1.3 Example 5 Comparative 24 Δ 15 ΔΔ Δ 1.6 Example 6

As apparent from the results shown in Table 2 described above, it hasbeen found that the media for electrophoretic display prepared inExamples 1 to 19 falling in the scope of the present invention areexcellent, as compared with the media for electrophoretic displayprepared in Comparative Examples 1 to 6 falling outside the scope of thepresent invention, in a reflectance on the white display face and thecolored display face and excellent as well in a hue of white display andcolored display which are visually observed and that they are free ofcoagulation and adhesion of the fine particles and excellent in aresponse and a contrast.

Next, the devices of a microcapsule type (MC) and a sheet type (S) forelectrophoretic display were prepared by methods described below, andevaluation of a reflectance on the white display face, visual evaluationof the white display face, evaluation of a reflectance on the coloreddisplay face, visual evaluation of the colored display face, evaluationof coagulation and adhesion of the fine particles and evaluation of theresponse and the contrast were carried out by the respective evaluationmethods described above.

The results obtained by evaluating the physical properties of thedevices for electrophoretic display are shown in the following Table 3.

Microcapsule Type Example 1

(1) Preparation of a Liquid for Electrophoretic Display

A dispersion of 100 g was prepared according to the formulationdescribed in Example 2 described above.

(2) Micro-Capsulation

A 5% by weight gelatin aqueous solution of 200 g and a 5% by weight gumarabic aqueous solution of 200 g were mixed while stirring and heated to50° C., and a pH of the solution was controlled to 9.0 by a sodiumhydroxide aqueous solution. The dispersion for electrophoretic displayprepared in (1) described above was added to the aqueous solution whileslowly stirring to prepare an emulsion.

Next, the pH was reduced to 4.0 by using an acetic acid aqueous solutionunder a prescribed stirring condition to form a gelatin/gum arabiccoacervate, and then it was cooled down to about 5° C. in about 30minutes.

Next, a 35% formalin aqueous solution of 10 g was added thereto, and thesolution was heated up to 50° C. to carry out curing reaction for about2 hours, whereby a slurry of microcapsules was prepared. Themicrocapsules thus obtained had a mean particle size of 80 μm.

(3) Evaluation of Device

A water-based urethane base binder solution of 1.5 part was mixed withthe microcapsule slurry of 1 part obtained in (2) described above, andthe mixture was coated on an ITO transparent electrode on a PET basematerial by means of an applicator coating machine and sufficientlydried under the condition of 50° C.

The cell for display was adhered on a counter electrode substrate andvacuum-pressed so that a gap between the counter electrodes was 60 μm toprepare a display device and evaluate it.

Microcapsule Type Example 2

(1) Preparation of a Liquid for Electrophoretic Display

A dispersion of 100 g was prepared according to the formulationdescribed in Example 9 described above.

(2) Micro-Capsulation

Hexamethylenediisocyanate (HDI) of 10 g was dissolved in the dispersion(1) described above, and then the solution was immediately added to a 5%by weight gelatin aqueous solution of 300 g under a prescribed stirringcondition to prepare an emulsion. The temperature was held at 35° C. tocontinue stirring for 2 hours, and then the temperature of the systemwas cooled down to 5° C.

Next, the pH was controlled to 9.0 by sodium hydroxide, and then a 25%glutaraldehyde aqueous solution of 10 g was added thereto. Thetemperature of the system was elevated up to 50° C., and capsulationreaction was finished in about 2 hours. The microcapsules thus obtainedhad a mean particle size of 90 μm.

(3) Evaluation of Device

A water-based silicon base binder solution of 2 parts containing aprescribed amount of a dielectric constant-controlling material wasmixed with the microcapsule slurry of 1 part obtained in (2) describedabove, and the mixture was coated on an ITO transparent electrode on aPET base material by means of an applicator coating machine andsufficiently dried under the condition of 50° C.

The cell for display was adhered on a counter electrode substrate andvacuum-pressed so that a gap between the counter electrodes was 60 μm toprepare a display device and evaluate it.

Microcapsule Type Example 3

(1) Preparation of a Liquid for Electrophoretic Display

A dispersion of 100 g was prepared according to the formulationdescribed in Example 10 described above.

(2) Micro-Capsulation

A buret body 10 g of HDI was dissolved in the dispersion (1) describedabove, and then the solution was immediately added to a 5% by weight PVAaqueous solution of 300 g under a prescribed stirring condition toprepare an emulsion. The temperature was held at 60° C. to continuestirring for 3 hours, and then the pH was controlled to 9.0 by sodiumhydroxide. Then, a 25% glutaraldehyde aqueous solution of 10 g was addedthereto. The temperature of the system was elevated up to 50° C., andcapsulation reaction was finished in about 2 hours. The microcapsulesthus obtained had a mean particle size of 75 μm.

(3) Evaluation of Device

A PVA base binder solution of 2 parts containing a prescribed amount ofa dielectric constant-controlling material was mixed with themicrocapsule slurry of 1 part obtained in (2) described above, and themixture was coated on an ITO transparent electrode on a PET basematerial by means of an applicator coating machine and sufficientlydried under the condition of 50° C.

The cell for display was adhered on a counter electrode substrate andvacuum-pressed so that a gap between the counter electrodes was 60 μm toprepare a display device and evaluate it.

Sheet Type Example 1

(1) Preparation of a Liquid for Electrophoretic Display

A dispersion of 100 g was prepared according to the formulationdescribed in Example 2 described above.

(2) Evaluation of Sheet Type Ink-Filled Spacer Device

An electrophoretic ink was filled in a sheet patterned on a size patternshown in FIG. 9, and this sheet was arranged on a counter electrode toan ITO transparent electrode on a PET base material to prepare a displaydevice and evaluate it. TABLE 3 Total evaluation Reflectance Visualevaluation Reflectance Visual evaluation Coagulation and on white ofwhite display on colored of colored adhesion of display face facedisplay face display face fine particles Response Contrast MC Example 135 ◯ 6 ◯ ◯ ◯ 6.6 MC Example 2 30 ◯ to Δ 7 ◯ ◯ ◯ 6.6 MC Example 3 28 ◯ toΔ 6 ◯ ◯ ◯ 7.1 S Example 1 30 ◯ to Δ 6 ◯ ◯ ◯ 7.0

As apparent from the results shown in Table 3 described above, it hasbeen found that the devices of the microcapsule type (MC) and the sheettype (S) for electrophoretic display are excellent in a reflectance onthe white display face and the colored display face and excellent aswell in a hue of white display and colored display which are visuallyobserved and that they are free of coagulation and adhesion of the fineparticles and excellent in a response and a contrast.

Examples 20 to 25 and Comparative Examples 7 to 11

Preparation of Liquids for Electrophoretic Display, the Second PresentInvention

Blend compositions of the respective examples and comparative examplesshown in the following Table 4 were dispersed for 60 minutes by means ofa paint shaker using glass beads to prepare liquids for electrophoreticdisplay.

Used were fine particles (A-1 and B-1), a colorant (dye), dispersionliquid media (C-1 and C-4), polyoxyethylene oxypropylene (POEOP) blockpolymers, a dispersant (D-2) and alkylpolyetheramines (E) each shownbelow.

Fine Particles A:

A-1: ITT-2 TiO₂ CR-50 (manufactured by Nikko Chemicals Co., Ltd.),titanium oxide treated the surface with a titan coupling agent, meanparticle size: about 0.4 μm

B-1: Rubcouleur 220(MD) Black (acryl copolymer colored beads,manufactured by Dainichiseika Color & Chemicals MFG. Co., Ltd.), meanparticle size: about 10 μm

Colorant (dye): Oil Blue N (manufactured by Wako Pure ChemicalIndustries, Ltd.)

Dispersion liquid medium C:

C-1: xylene

C-4: Nisseki Hisol SAS296 (diallylalkane, manufactured by NipponPetrochemicals Co., Ltd.)

Polyoxyethylene Oxypropylene (POEOP) Block Polymer F:

F-1: Pronon 102 (average molecular weight: 1250, ethylene oxide amount:20% by weight, manufactured by NOF Corporation)

F-2: Pronon 104 (average molecular weight: 1670, ethylene oxide amount:40% by weight, manufactured by NOF Corporation)

F-3: Pronon 201 (average molecular weight: 2220, ethylene oxide amount:10% by weight, manufactured by NOF Corporation)

F-4: Pronon 204 (average molecular weight: 3300, ethylene oxide amount:40% by weight, manufactured by NOF Corporation)

F-5: Pronon 208 (average molecular weight: 10000, ethylene oxide amount:80% by weight, manufactured by NOF Corporation)

Dispersant D:

D-2: sorbitan trioleate

Alkylpolyetheramine E:

E-1: Nymeen L-201 (manufactured by NOF Corporation),hydroxyethyllaurylamine

E-3: Nymeen S-202 (manufactured by NOF Corporation), polyethylene glycolstearylamine

E-5: Nymeen DT-203 (manufactured by NOF Corporation), polyoxyethylenealkyl(beef tallow)propylenediamine

E-6: trioctylamine TABLE 4 (Blend unit: % by weight, total amount: 100)Fine particle Dispersion liquid media POEOP block Dispersant Alkylpoly-A-1 B-1 Colorant C-1 C-4 polymer F D-2 etheramine E Example 20 10 — 0.116.0 63.9 F-3 5 — E-3 5 Example 21 10 5 — 15.4 61.6 F-1 3 — E-1 5Example 22 10 5 — 23.1 53.9 F-2 3 — E-1 5 Example 23 10 5 — 15.4 61.6F-3 3 — E-3 5 Example 24 10 5 — 18.4 56.6 F-4 5 — E-3 5 Example 25 10 5— 19.4 56.6 F-3 3 1 E-3 5 Comparative 10 — 0.1 24.6 57.3 — 5 E-3 3Example 7 Comparative 10 — 0.1 16.4 65.5 F-3 5 — E-5 3 Example 8Comparative 10 5 — 15.4 61.6 F-5 3 — E-3 5 Example 9 Comparative 10 5 —22.5 52.5 F-3 5 — E-6 5 Example 10 Comparative 10 5 — 15.4 61.6 — 5 E-53 Example 11

The respective liquids for electrophoretic display obtained according tothe formulation shown in Table 4 described above were used to preparemedia for electrophoretic display by the same method as in Example 1described above, and evaluation of a reflectance on the white displayface, visual evaluation of the white display face, evaluation of areflectance on the colored display face, visual evaluation of thecolored display face, evaluation of coagulation and adhesion of the fineparticles and evaluation of the response and the contrast were carriedout by the respective evaluation methods described above. In additionthereto, coagulation and adhesion of the fine particles, the responseand the contrast after stored at 50° C. for 1M (one month) wereevaluated by the following evaluation methods.

The results obtained by evaluating the physical properties of the mediafor electrophoretic display are shown in the following Table 5.

Evaluation Methods of Coagulation and Adhesion of the Fine Particles,the Response and the Contrast After Stored at 50° C. for 1M (One Month):

The respective media for electrophoretic display prepared in Examples 20to 25 and Comparative Examples 7 to 11 by the method described abovewere evaluated for coagulation and adhesion of the fine particles, aresponse and a contrast after stored at 50° C. for 1M (one month) by therespective evaluation methods described above. TABLE 5 Visual VisualCoagulation Coagulation Reflectance evaluation evaluation and of fineResponse Contrast on white of white Reflectance of colored adhesionparticles, after after display display on colored display of fine afterstored stored stored face face display face face particles ResponseContrast 50° C., 1M 50° C., 1M 50° C., 1M Example 20 34 ◯ to Δ 8 ◯ to Δ◯ ◯ 4.3 ◯ ◯ 4.3 Example 21 52 ◯ 6 ◯ ◯ ◯ to Δ 8.7 ◯ ◯ to Δ 8.6 Example 2253 ◯ 7 ◯ ◯ ◯ 7.6 ◯ ◯ 7.7 Example 23 55 ◯ 7 ◯ ◯ ◯ 7.9 ◯ ◯ 7.9 Example 2450 ◯ 6 ◯ ◯ ◯ 8.3 ◯ ◯ 8.3 Example 25 55 ◯ 6 ◯ ◯ ◯ 9.2 ◯ ◯ 9.1 Comparative32 ◯ to Δ 8 ◯ to Δ ◯ ◯ 4.0 Δ Δ 3.1 Example 7 Comparative 30 ◯ to Δ 8 Δ ◯◯ 3.8 Δ Δ 3.0 Example 8 Comparative 40 ◯ 7 Δ ◯ to Δ ◯ to Δ 5.7 Δ Δ 4.5Example 9 Comparative 42 ◯ 7 Δ ◯ to Δ ◯ to Δ 6.0 Δ Δ 4.3 Example 10Comparative 30 Δ 6 Δ ◯ to Δ Δ 5.0 X X 3.8 Example 11

As apparent from the results shown in Table 5 described above, it hasbeen found that the media for electrophoretic display prepared inExamples 20 to 25 falling in the scope of the present invention areexcellent, as compared with the media for electrophoretic displayprepared in Comparative Examples 7 to 11 falling outside the scope ofthe present invention, in a reflectance on the white display face andthe colored display face and excellent as well in a hue of white displayand colored display which are visually observed and that they are freeof coagulation and adhesion of the fine particles and excellent in aresponse and a contrast and in addition thereto, they are free ofcoagulation and adhesion of the fine particles and excellent in aresponse and a contrast even after stored at 50° C. for 1M (one month).

Next, the devices of a microcapsule type (MC) and a sheet type (S) forelectrophoretic display were prepared by methods described below, andevaluation of a reflectance on the white display face, visual evaluationof the white display face, evaluation of a reflectance on the coloreddisplay face, visual evaluation of the colored display face, evaluationof coagulation and adhesion of the fine particles and evaluation of theresponse and the contrast and evaluation of coagulation and adhesion ofthe fine particles, the response and the contrast after stored at 50° C.for 1M (one month) were carried out by the respective evaluation methodsdescribed above.

The results obtained by evaluating the physical properties of the abovedevices for electrophoretic display are shown in the following Table 6.

Microcapsule Type Example 4

(1) Preparation of a Liquid for Electrophoretic Display

A dispersion of 100 g was prepared according to the formulationdescribed in Example 20 described above.

(2) Micro-Capsulation

A 5% by weight gelatin aqueous solution of 200 g and a 5% by weight gumarabic aqueous solution of 200 g were mixed while stirring and heated to50° C., and a pH of the solution was controlled to 9.0 by a sodiumhydroxide aqueous solution. The dispersion for electrophoretic displayprepared in (1) described above was added to the aqueous solution whileslowly stirring to prepare an emulsion.

Then, the pH was reduced to 4.0 by using an acetic acid aqueous solutionunder a prescribed stirring condition to form a gelatin/gum arabiccoacervate, and then it was cooled down to about 5° C. in about 30minutes.

Next, a 35% formalin aqueous solution of 10 g was added thereto, and thesolution was heated up to 50° C. to carry out curing reaction for about2 hours, whereby a slurry of microcapsules was prepared. Themicrocapsules thus obtained had a mean particle size of 80 μm.

(3) Evaluation of Device

A water-based urethane base binder solution of 1.5 part was mixed withthe microcapsule slurry of 1 part obtained in (2) described above, andthe mixture was coated on an ITO transparent electrode on a PET basematerial by means of an applicator coating machine and sufficientlydried under the condition of 50° C.

The above cell for display was adhered on a counter electrode substrateand vacuum-pressed so that a gap between the counter electrodes was 60μm to prepare a display device and evaluate it.

Microcapsule Type Example 5

(1) Preparation of a Liquid for Electrophoretic Display

A dispersion of 100 g was prepared according to the formulationdescribed in Example 21 described above.

(2) Micro-Capsulation

Hexamethylenediisocyanate (HDI) of 10 g was dissolved in the dispersion(1) described above, and then the solution was immediately added to a 5%by weight gelatin aqueous solution of 300 g under a prescribed stirringcondition to prepare an emulsion. The temperature was held at 35° C. tocontinue stirring for 2 hours, and then the temperature of the systemwas cooled down to 5° C.

Next, the pH was controlled to 9.0 by sodium hydroxide, and then a 25%glutaraldehyde aqueous solution of 10 g was added thereto. Thetemperature of the system was elevated up to 50° C., and capsulationreaction was finished in about 2 hours. The microcapsules thus obtainedhad a mean particle size of 90 μm.

(3) Evaluation of Device

A water-based silicon base binder solution of 2 parts containing aprescribed amount of a dielectric constant-controlling material wasmixed with the microcapsule slurry of 1 part obtained in (2) describedabove, and the mixture was coated on an ITO transparent electrode on aPET base material by means of an applicator coating machine andsufficiently dried under the condition of 50° C.

The cell for display was adhered on a counter electrode substrate andvacuum-pressed so that a gap between the counter electrodes was 60 μm toprepare a display device and evaluate it.

Microcapsule Type Example 6

(1) Preparation of a Liquid for Electrophoretic Display

A dispersion of 100 g was prepared according to the formulationdescribed in Example 22 described above.

(2) Micro-Capsulation

A buret form of HDI of 10 g was dissolved in the dispersion (1)described above, and then the solution was immediately added to a 5% byweight PVA aqueous solution of 300 g under a prescribed stirringcondition to prepare an emulsion. The temperature was held at 60° C. tocontinue stirring for 3 hours, and then the pH was controlled to 9.0 bysodium hydroxide. Then, a 25% glutaraldehyde aqueous solution of 10 gwas added thereto. The temperature of the system was elevated up to 50°C., and capsulation reaction was finished in about 2 hours. Themicrocapsules thus obtained had a mean particle size of 75 μm.

(3) Evaluation of Device

A PVA base binder solution of 2 parts containing a prescribed amount ofa dielectric constant-controlling material was mixed with themicrocapsule slurry of 1 part obtained in (2) described above, and themixture was coated on an ITO transparent electrode on a PET basematerial by means of an applicator coating machine and sufficientlydried under the condition of 50° C.

The cell for display was adhered on a counter electrode substrate andvacuum-pressed so that a gap between the counter electrodes was 60 μm toprepare a display device and evaluate it.

Sheet Type Example 2

(1) Preparation of a Liquid for Electrophoretic Display

A dispersion of 100 g was prepared according to the formulationdescribed in Example 23 described above.

(2) Evaluation of a Sheet Type Ink-Filled Spacer Device

An electrophoretic ink was filled in a sheet patterned on a size patternshown in FIG. 9, and this sheet was arranged on a counter electrode toan ITO transparent electrode on a PET base material to prepare a displaydevice and evaluate it. TABLE 6 Visual Visual Coagulation CoagulationReflectance evaluation evaluation and of fine Response Contrast on whiteof white Reflectance of colored adhesion particles after after displaydisplay on colored display of fine after stored stored stored face facedisplay face face particles Response Contrast 50° C., 1M 50° C., 1M 50°C., 1M MC Example 4 32 ◯ to Δ 7 ◯ to Δ ◯ ◯ 4.0 ◯ ◯ 4.0 MC Example 5 50 ◯6 ◯ ◯ ◯ to Δ 8.1 ◯ ◯ to Δ 8.1 MC Example 6 50 ◯ 6 ◯ ◯ ◯ 7.1 ◯ ◯ 7.2 SExample 2 53 ◯ 7 ◯ ◯ ◯ 7.6 ◯ ◯ 7.6

As apparent from the results shown in Table 6 described above, it hasbeen found that the devices of the microcapsule type (MC) and the sheettype (S) for electrophoretic display are excellent in a reflectance on awhite display face and a colored display face and excellent as well in ahue of white display and colored display which are visually observed;they are free of coagulation and adhesion of the fine particles andexcellent in a response and a contrast; and in addition thereto, theyare free of coagulation and adhesion of the fine particles and excellentin a response and a contrast even after stored at 50° C. for 1M (onemonth).

Examples 26 to 30 and Comparative Examples 12 to 16

Preparation of Liquids for Electrophoretic Display, the Third Invention

Blend compositions of the respective examples and comparative examplesshown in the following Table 7 were dispersed for 60 minutes by means ofa paint shaker using glass beads to prepare liquids for electrophoreticdisplay.

Used were fine particles (A-1 and B-1), a colorant (dye), dispersionliquid media (C-1 and C-4), acetylene derivatives (G-1 to G-2), apolyoxyethylene oxypropylene (POEOP) block polymer F, a dispersant D andalkylpolyetheramine E each shown below.

Fine Particles A:

A-1: ITT-2 TiO₂ CR-50 (manufactured by Nikko Chemicals Co., Ltd.),titanium oxide treated the surface with a titan coupling agent, meanparticle size: about 0.4 μm

B-1: Rubcouleur 220(MD) Black (acryl copolymer colored beads,manufactured by Dainichiseika Color & Chemicals MFG. Co., Ltd.), meanparticle size: about 10 μm

Colorant (dye): Oil Blue N (manufactured by Wako Pure ChemicalIndustries, Ltd.)

Dispersion Liquid Medium C:

C-1: xylene

C-4: Nisseki Hisol SAS296 (diarylalkane, manufactured by NipponPetrochemicals Co., Ltd.)

Acetylene Derivative G:

G-1: Surfynol 104DPM (HLB: 4, manufactured by Nissin Chemical IndustryCo., Ltd.)

G-2: Surfynol DF110D (HLB: 3, manufactured by Nissin Chemical IndustryCo., Ltd.)

Polyoxyethylene Oxypropylene (POEOP) Block Polymer F:

Pronon 102 (average molecular weight: 1250, ethylene

oxide amount: 20% by weight, manufactured by NOF Corporation)

Dispersant D: Sorbitan Trioleate

Alkylpolyetheramine E: Nymeen L-201 (manufactured by NOF Corporation),hydroxyethyllaurylamine TABLE 7 Hydrophilization Fine particleDispersion liquid media C Acetylene POEOP block Dispersant Alkylpoly-treatment to A-1 B-1 Colorant C-1 C-4 derivative G polymer F Detheramine E substrate Example 26 10 — 0.1 40.4 40.4 D-1 0.1 5.0 — 4.0 —Example 27 15 7.5 — 34.7 34.7 D-1 0.1 3.0 — 5.0 — Example 28 15 7.5 —34.2 34.2 D-2 0.1 4.0 — 5.0 — Example 29 15 7.5 — 33.2 33.2 D-2 0.1 5.01.0 5.0 Ozone treatment Example 30 15 7.5 — 34.7 34.7 D-2 0.1 3.0 1.04.0 UV itoro treatment Comparative 15 — 0.1 37.9 38.0 — 5.0 — 4.0 —Example 12 Comparative 15 7.5 — 34.7 34.8 — 3.0 — 5.0 — Example 13Comparative 15 7.5 — 34.2 34.3 — 4.0 — 5.0 — Example 14 Comparative 157.5 — 33.2 33.3 — 5.0 1.0 5.0 — Example 15 Comparative 15 7.5 — 34.734.8 — 3.0 1.0 4.0 — Example 16

The respective liquids for electrophoretic display obtained according tothe formulation shown in Table 7 described above were used to preparemedia for electrophoretic display by methods described below, andevaluation of a reflectance on the white display face, visual evaluationof the white display face, evaluation of a reflectance on the coloreddisplay face, visual evaluation of the colored display face, evaluationof coagulation and adhesion of the fine particles and evaluation of theresponse and the contrast were carried out by the respective evaluationmethods described above. Further, the display characteristics(coagulation and adhesion, contrast) after repetitive display(frequency: 1000 times, 5000 times and 10000 times) were evaluated bythe following evaluation methods, and coagulation and adhesion of thefine particles and the response and the contrast after stored at 50° C.for 1M (one month) were evaluated by the evaluation methods describedabove.

The results obtained by evaluating the physical properties of the mediafor electrophoretic display are shown in the following Table 8.

Preparation of Media for Electrophoretic Display Using the Liquids forElectrophoretic Display:

Glass substrates (thickness: 1.1 mm) in which a transparent conductivefilm (ITO film) was formed in a thickness of 0.15 μm on one surface wereused as a substrate in which an electrode was provided on one surface,and a pair of the above glass substrates were oppositely disposed viaspacers of about 100 μm to form a cell. Also, cells were formed in someof the tests using glass substrate subjected to ozone treatment and UVitoro treatment in order to observe the effect of hydrophilizationtreatment of the substrate electrode. In the ozone treatment, the glasssubstrates obtained above were subjected to ozone treatment (MitsubishiOzonizer OS-IN, manufactured by Mitsubishi Electric Corporation) at anozone concentration of 20 g/m³ for 60 minutes. In the UV itorotreatment, a fuel gas containing 0.0001 mole % of tetramethylsilanehaving a boiling point of 27° C. and 0.00001 mole % oftetramethoxysilane having a boiling point of 122° C. was used as a fuelgas to subject the glass substrate to silicification flame treatment for0.5 second.

The liquids for electrophoretic display prepared according to theformulations shown in Table 7 described above were filled into the abovespace to thereby prepare media for electrophoretic display.

Evaluating Method of Repetitive Display Characteristics (Coagulation andContrast):

The repetitive display characteristics were evaluated for coagulationand the contrast, and the display states in carrying out display 1000times, 5000 times and 10000 times were evaluated according to thefollowing evaluation criteria.

Evaluation Criteria:

◯: no change from the initial state

Δ: coagulation and adhesion are partially observed on the electrode, andthe contrast is a little deteriorated

X: coagulation and adhesion are heavily observed, and the contrast isnotably deteriorated TABLE 8 Visual Reflec- Reflec- evalua- tance VisualInitial tance tion of on evaluation coagulation Repetitive displaycharacter- on white white colored of colored & adhesion istic(coagulation, contrast) display display display display of fine 10005000 10000 After stored 50° C., 1M face face face face particlesResponse Contrast times times times Response Contrast Example 26 34 ◯ toΔ 8 ◯ to Δ ◯ ◯ 4.3 ◯ ◯ ◯ to Δ ◯ 4.3 Example 27 52 ◯ 6 ◯ ◯ ◯ 9.0 ◯ ◯ ◯ toΔ ◯ 8.9 Example 28 55 ◯ 8 ◯ ◯ ◯ 8.1 ◯ ◯ ◯ to Δ ◯ 8.0 Example 29 54 ◯ 7 ◯◯ ◯ 8.2 ◯ ◯ ◯ ◯ 8.2 Example 30 56 ◯ 7 ◯ ◯ ◯ 8.9 ◯ ◯ ◯ ◯ 9.0 Comparative34 ◯ to Δ 8 ◯ to Δ ◯ ◯ 4.3 Δ Δ X ◯ 4.3 Example 12 Comparative 51 ◯ 6 ◯ ◯◯ 8.9 Δ Δ X ◯ 8.9 Example 13 Comparative 54 ◯ 7 ◯ ◯ ◯ 8.0 Δ Δ X ◯ 8.1Example 14 Comparative 53 ◯ 7 ◯ ◯ ◯ 8.1 Δ Δ X ◯ 7.9 Example 15Comparative 54 ◯ 7 ◯ ◯ ◯ 9.0 Δ Δ X ◯ 8.8 Example 16

As apparent from the results shown in Table 8 described above, it hasbeen found that the media for electrophoretic display prepared inExamples 26 to 30 falling in the scope of the present invention areexcellent, as compared with the media for electrophoretic displayprepared in Comparative Examples 12 to 16 falling outside the scope ofthe present invention, in a reflectance on a white display face and acolored display face and excellent as well in a hue of white display andcolored display which are visually observed; they are free ofcoagulation and adhesion of the fine particles and excellent in aresponse and a contrast; in the repetitive display characteristics of1000 times, 5000 times and 10000 times, they are free of coagulation andadhesion and excellent in a contrast; and in addition thereto, they arefree of coagulation and adhesion of the fine particles and excellent ina response and a contrast even after stored at 50° C. for 1M (onemonth).

Next, the devices of a microcapsule type (MC) and a sheet type (S) forelectrophoretic display were prepared by methods described below, andevaluation of a reflectance on the white display face, visual evaluationof the white display face, evaluation of a reflectance on the coloreddisplay face, visual evaluation of the colored display face, evaluationof coagulation and adhesion of the fine particles and evaluation of theresponse and the contrast, evaluation of the display characteristics(coagulation and adhesion, contrast) after repetitive display(frequency: 1000 times, 5000 times and 10000 times) and evaluation ofcoagulation and adhesion of the fine particles, the response and thecontrast after stored at 50° C. for 1M (one month) were carried out bythe respective evaluation methods described above.

The results obtained by evaluating the physical properties of the abovedevices for electrophoretic display are shown in the following Table 9.

Microcapsule Type Example 7

(1) Preparation of a Liquid for Electrophoretic Display

A dispersion of 100 g was prepared according to the formulationdescribed in Example 27 described above.

(2) Micro-Capsulation

A 5% by weight gelatin aqueous solution of 200 g and a 5% by weight gumarabic aqueous solution of 200 g were mixed while stirring and heated to50° C., and a pH of the solution was controlled to 9.0 by a sodiumhydroxide aqueous solution. The dispersion for electrophoretic displayprepared in (1) described above was added to the aqueous solution whileslowly stirring to prepare an emulsion.

Then, the pH was reduced to 4.0 by using an acetic acid aqueous solutionunder a prescribed stirring condition to form a gelatin/gum arabiccoacervate, and then it was cooled down to about 5° C. in about 30minutes.

Next, a 35% formalin aqueous solution of 10 g was added thereto, and thesolution was heated up to 50° C. to carry out curing reaction for about2 hours, whereby a slurry of a microcapsule was prepared. Themicrocapsules thus obtained had a mean particle size of 80 μm.

(3) Evaluation of Device

A water-based urethane base binder solution of 1.5 part was mixed withthe microcapsule slurry of 1 part obtained in (2) described above, andthe mixture was coated on an ITO transparent electrode on a PET basematerial by means of an applicator coating machine and sufficientlydried under the condition of 50° C.

The cell for display was adhered on a counter electrode substrate andvacuum-pressed so that a gap between the counter electrodes was 60 μm toprepare a display device and evaluate it.

Sheet Type Example 13

(1) Preparation of a Liquid for Electrophoretic Display

A liquid for electrophoretic display of 100 g was prepared according tothe formulation described in Example 2 described above.

(2) Evaluation of a Sheet Type Ink-Filled Spacer Device

The liquid for electrophoretic display was filled in a cell sheet havinga cell gap of 80 μm in which patterns were formed on an ITO transparentelectrode on a PET base material on a size pattern shown in FIG. 9 by aphotoetching method, and a counter electrode was arranged thereon andsealed by a UV curing adhesive (UV3400, manufactured by Toagosei Co.,Ltd., hereinafter the same shall apply) to prepare a display device andevaluate it.

Sheet Type Example 14

(1) Preparation of a Liquid for Electrophoretic Display

A liquid for electrophoretic display of 100 g was prepared according tothe formulation described in Example 28 described above.

(2) Evaluation of a Sheet Type Ink-Filled Spacer Device

The liquid for electrophoretic display was filled in a polyimide-madecell sheet having a thickness of 50 μm which was patterned on a sizepattern shown in FIG. 9 by a laser beam machining method, and a counterelectrode were arranged thereon and sealed by the UV curing adhesive toprepare a display device and evaluate it.

Sheet Type Example 15

In the sheet type Example 13 described above, the ITO transparentelectrode on which the cell patterns were formed and the counterelectrode were subjected to ozone treatment (Mitsubishi Ozonizer OS-IN,manufactured by Mitsubishi Electric Corporation) at an ozoneconcentration of 20 g/m³ for 60 minutes, and then the liquid forelectrophoretic display was filled therein to prepare a display device.

Sheet Type Example 16

In the sheet type Example 14 described above, the ITO transparentelectrode, the cell sheet and the counter electrode were subjected to UVitoro treatment, and then the liquid for electrophoretic display wasfilled therein to prepare a display device. TABLE 9 Visual Reflec-Reflec- evalua- tance Visual Initial tance tion of on evaluationcoagulation Repetitive display character- on white white colored ofcolored & adhesion istic (coagulation, contrast) display display displaydisplay of fine Re- Con- 1000 5000 10000 After stored 50° C., 1M faceface face face particles sponse trast times times times ResponseContrast MC Example 7 50 ◯ 6 ◯ ◯ ◯ to Δ 8.0 ◯ ◯ ◯ ◯ 7.9 S Example 13 51◯ 6 ◯ ◯ ◯ 8.7 ◯ ◯ ◯ ◯ 8.6 S Example 14 53 ◯ 8 ◯ ◯ ◯ 7.9 ◯ ◯ ◯ ◯ 7.9 SExample 15 53 ◯ 8 ◯ ◯ ◯ 7.9 ◯ ◯ ◯ ◯ 7.9 S Example 16 53 ◯ 8 ◯ ◯ ◯ 8.0 ◯◯ ◯ ◯ 7.9

As apparent from the results shown in Table 9 described above, it hasbeen found that the devices of the microcapsule type (MC) and the sheettype (S) for electrophoretic display are excellent in a reflectance on awhite display face and a colored display face and excellent as well in ahue of white display and colored display which are visually observed;they are free of coagulation and adhesion of the fine particles andexcellent in a response and a contrast; in the repetitive displaycharacteristics of 1000 times, 5000 times and 10000 times, they are freeof coagulation and adhesion and excellent in a contrast; and in additionthereto, they are free of coagulation and adhesion of the fine particlesand excellent in a response and a contrast even after stored at 50° C.for 1M (one month).

INDUSTRIAL APPLICABILITY

The display liquid for electrophoretic display thus constitutedaccording to the present invention and the display medium and thedisplay device each using the same can realize display having a highcontrast and can display the contrast with high reliability even inrepetitive display because of excellent dispersion stability of thedisplay liquid for electrophoretic display, and they are excellent aswell in a response, so that they can suitably be applied as portabletype display devices for information terminal equipment, electronicprice tags and electronic books.

1-24. (canceled)
 25. A liquid for electrophoretic display comprising atleast alkylpolyetheramine having a structural unit represented by thefollowing Formula (I), one or more kinds of fine particles, a dispersantand a dispersion liquid medium, wherein the fine particles describedabove contain fine particles subjected to surface treatment for makinglipophilic:

in Formula (I) described above, R₁ is a saturated hydrocarbon group oran unsaturated hydrocarbon group; R₂ is (CH₂CH₂O)x-H; R₃ is(CH₂CH₂O)y-H; and x and y are positive numbers.
 26. A liquid forelectrophoretic display comprising at least alkylpolyetheramine having astructural unit represented by the following Formula (I), apolyoxyethylene oxypropylene block polymer having a structural unitrepresented by the following Formula (II), one or more kinds of fineparticles and a dispersion liquid medium:

in Formula (I) described above, R₁ is a saturated hydrocarbon group oran unsaturated hydrocarbon group; R₂ is (CH₂CH₂O)x-H; R₃ is(CH₂CH₂O)y-H; and x and y are positive numbers;OH(C₂H₄O)p(C₃H₆O)qH  (II) in Formula (II) described above, p and q arepositive numbers.
 27. The liquid for electrophoretic display asdescribed in claim 26, further comprising an acetylene derivative havinga structural unit represented by the following Formula (III):

in Formula (III) described above, R₄ and R₅ are a saturated hydrocarbongroup or an unsaturated hydrocarbon group; R₆ is OCH₂CH(CH₃)OH or(OCH₂CH₂)m-OH; R₇ is OCH₂CH(CH₃)OH or (OCH₂CH₂)n-OH; m and n are 0 orpositive numbers; and R₆ and R₇ may be the same or different.
 28. Theliquid for electrophoretic display as described in claim 26, wherein thepolyoxyethylene oxypropylene block polymer has an average molecularweight of 1,000 to 4,000.
 29. The liquid for electrophoretic display asdescribed in claim 27, wherein the polyoxyethylene oxypropylene blockpolymer has an average molecular weight of 1,000 to 4,000.
 30. Theliquid for electrophoretic display as described in claim 26, wherein anamount of ethylene oxide in the polyoxyethylene oxypropylene blockpolymer is 50% by weight or less.
 31. The liquid for electrophoreticdisplay as described in claim 27, wherein an amount of ethylene oxide inthe polyoxyethylene oxypropylene block polymer is 50% by weight or less.32. The liquid for electrophoretic display as described in claim 26,wherein a content of the polyoxyethylene oxypropylene block polymer is0.01 to 30% by weight based on the total amount of the display liquid.33. The liquid for electrophoretic display as described in claim 27,wherein a content of the polyoxyethylene oxypropylene block polymer is0.01 to 30% by weight based on the total amount of the display liquid.34. The liquid for electrophoretic display as described in claim 27,wherein an HLB of the acetylene derivative is 10 or less.
 35. The liquidfor electrophoretic display as described in claim 26, wherein the fineparticles are subjected to surface treatment for making the fineparticles lipophilic.
 36. The liquid for electrophoretic display asdescribed in claim 27, wherein the fine particles are subjected tosurface treatment for making the fine particles lipophilic.
 37. Theliquid for electrophoretic display as described in claim 25, wherein thesurface treatment for making the fine particles lipophilic is carriedout with a coupling agent.
 38. The liquid for electrophoretic display asdescribed in claim 26, wherein the surface treatment for making the fineparticles lipophilic is carried out with a coupling agent.
 39. Theliquid for electrophoretic display as described in claim 27, wherein thesurface treatment for making the fine particles lipophilic is carriedout with a coupling agent.
 40. The liquid for electrophoretic display asdescribed in claim 37, wherein the coupling agent is at least one agentselected from the group consisting of titanate base coupling agents,aluminum base coupling agents and silane base coupling agents.
 41. Theliquid for electrophoretic display as described in claim 38, wherein thecoupling agent is at least one agent selected from the group consistingof titanate base coupling agents, aluminum base coupling agents andsilane base coupling agents.
 42. The liquid for electrophoretic displayas described in claim 39, wherein the coupling agent is at least oneagent selected from the group consisting of titanate base couplingagents, aluminum base coupling agents and silane base coupling agents.43. The liquid for electrophoretic display as described in claim 25,wherein a surface functional group of the fine particles subjected tothe surface treatment for making the fine particles lipophilic is analkoxycarbonyl group.
 44. The liquid for electrophoretic display asdescribed in claim 26, wherein a surface functional group of the fineparticles subjected to the surface treatment for making the fineparticles lipophilic is an alkoxycarbonyl group.
 45. The liquid forelectrophoretic display as described in claim 27, wherein a surfacefunctional group of the fine particles subjected to the surfacetreatment for making the fine particles lipophilic is an alkoxycarbonylgroup.
 46. The liquid for electrophoretic display as described in claim25, wherein a content of the alkylpolyetheramine is 1.0 to 200% byweight based on a content of the fine particles.
 47. The liquid forelectrophoretic display as described in claim 26, wherein a content ofthe alkylpolyetheramine is 1.0 to 200% by weight based on a content ofthe fine particles.
 48. The liquid for electrophoretic display asdescribed in claim 27, wherein a content of the alkylpolyetheramine is1.0 to 200% by weight based on a content of the fine particles.
 49. Theliquid for electrophoretic display as described in claim 25, wherein atleast one kind of the fine particles is polymer fine particlescontaining a colorant, an organic pigment or an inorganic pigment. 50.The liquid for electrophoretic display as described in claim 26, whereinat least one kind of the fine particles is polymer fine particlescontaining a colorant, an organic pigment or an inorganic pigment. 51.The liquid for electrophoretic display as described in claim 27, whereinat least one kind of the fine particles is polymer fine particlescontaining a colorant, an organic pigment or an inorganic pigment. 52.The liquid for electrophoretic display as described in claim 49, whereina structural component of the polymer fine particles containing acolorant is a cross-linked acryl base resin.
 53. The liquid forelectrophoretic display as described in claim 50, wherein a structuralcomponent of the polymer fine particles containing a colorant is across-linked acryl base resin.
 54. The liquid for electrophoreticdisplay as described in claim 51, wherein a structural component of thepolymer fine particles containing a colorant is a cross-linked acrylbase resin.
 55. The liquid for electrophoretic display as described inclaim 25, wherein the fine particles have a mean particle size of 0.05to 20 μm.
 56. The liquid for electrophoretic display as described inclaim 26, wherein the fine particles have a mean particle size of 0.05to 20 μm.
 57. The liquid for electrophoretic display as described inclaim 27, wherein the fine particles have a mean particle size of 0.05to 20 μm.
 58. The liquid for electrophoretic display as described inclaim 26, further comprising a dispersant.
 59. The liquid forelectrophoretic display as described in claim 27, further comprising adispersant.
 60. The liquid for electrophoretic display as described inclaim 25, wherein the dispersant is a nonionic or anionic surfactant.61. The liquid for electrophoretic display as described in claim 26,wherein the dispersant is a nonionic or anionic surfactant.
 62. Theliquid for electrophoretic display as described in claim 27, wherein thedispersant is a nonionic or anionic surfactant.
 63. The liquid forelectrophoretic display as described in claim 25, wherein a content ofthe dispersant is 0.01 to 50% by weight based on the total amount of thedisplay liquid.
 64. The liquid for electrophoretic display as describedin claim 26, wherein a content of the dispersant is 0.01 to 50% byweight based on the total amount of the display liquid.
 65. The liquidfor electrophoretic display as described in claim 27, wherein a contentof the dispersant is 0.01 to 50% by weight based on the total amount ofthe display liquid.
 66. A medium for electrophoretic display wherein theliquid for electrophoretic display as described in claim 25 is filledinto independent structures of microcapsules or cells in the medium. 67.A medium for electrophoretic display wherein the liquid forelectrophoretic display as described in claim 26 is filled intoindependent structures of microcapsules or cells in the medium.
 68. Amedium for electrophoretic display wherein the liquid forelectrophoretic display as described in claim 27 is filled intoindependent structures of microcapsules or cells in the medium.
 69. Themedium for electrophoretic display as described in claim 66, wherein inthe structure of the cell filled with the liquid for electrophoreticdisplay, an electrode part and a cell part that the liquid forelectrophoretic display touches are subjected to hydrophilizationtreatment selected from the group consisting of ozone treatment, plasmatreatment, corona treatment, UV itoro treatment, sputtering treatment,polymer layer-forming treatment, inorganic layer-forming treatment andorganic or inorganic hybrid layer-forming treatment.
 70. The medium forelectrophoretic display as described in claim 67, wherein in thestructure of the cell filled with the liquid for electrophoreticdisplay, an electrode part and a cell part that the liquid forelectrophoretic display touches are subjected to hydrophilizationtreatment selected from the group consisting of ozone treatment, plasmatreatment, corona treatment, UV itoro treatment, sputtering treatment,polymer layer-forming treatment, inorganic layer-forming treatment andorganic or inorganic hybrid layer-forming treatment.
 71. The medium forelectrophoretic display as described in claim 68, wherein in thestructure of the cell filled with the liquid for electrophoreticdisplay, an electrode part and a cell part that the liquid forelectrophoretic display touches are subjected to hydrophilizationtreatment selected from the group consisting of ozone treatment, plasmatreatment, corona treatment, UV itoro treatment, sputtering treatment,polymer layer-forming treatment, inorganic layer-forming treatment andorganic or inorganic hybrid layer-forming treatment.
 72. The medium forelectrophoretic display as described in claim 66, wherein themicrocapsule has a size of 10 to 200 μm.
 73. The medium forelectrophoretic display as described in claim 67, wherein themicrocapsule has a size of 10 to 200 μm.
 74. The medium forelectrophoretic display as described in claim 68, wherein themicrocapsule has a size of 10 to 200 μm.
 75. The medium forelectrophoretic display as described in claim 66, wherein themicrocapsule has flexibility and is less liable to generate a space inarranging the microcapsules.
 76. The medium for electrophoretic displayas described in claim 67, wherein the microcapsule has flexibility andis less liable to generate a space in arranging the microcapsules. 77.The medium for electrophoretic display as described in claim 68, whereinthe microcapsule has flexibility and is less liable to generate a spacein arranging the microcapsules.
 78. The medium for electrophoreticdisplay as described in claim 66, wherein the independent cells have avolume of 1×10⁻⁹ to 1×10⁻³ ml.
 79. The medium for electrophoreticdisplay as described in claim 67, wherein the independent cells have avolume of 1×10⁻⁹ to 1×10⁻³ ml.
 80. The medium for electrophoreticdisplay as described in claim 68, wherein the independent cells have avolume of 1×10⁻⁹ to 1×10⁻³ ml.
 81. An electrophoretic display devicecomprising a pair of substrates in which a light-transmitting electrodeis formed on at least one substrate and the medium for electrophoreticdisplay as described in claim 66 interposed between the abovesubstrates.
 82. An electrophoretic display device comprising a pair ofsubstrates in which a light-transmitting electrode is formed on at leastone substrate and the medium for electrophoretic display as described inclaim 67 interposed between the above substrates.
 83. An electrophoreticdisplay device comprising a pair of substrates in which alight-transmitting electrode is formed on at least one substrate and themedium for electrophoretic display as described in claim 68 interposedbetween the above substrates.